This will be my last reply in this thread because I don't think I can help or add any value. If after this you are still locked into your opinion, then it is pointless to keep debating this, regardless of how friendly we keep it.
The ONE thing you can blame on SAI is their advertising, but NOT how you think. Their advertising is very accurate. UPB
is much more reliable than x-10 or other technologies. It
is 99.9 reliable. I proved that myself a long time ago. It was a situation where x-10 would not work at all, even on the same circuit with everything else off and everything else disconnected from the circuit. I can't, and won't, try to explain it or try to figure it out again, but that was the fact. Now try UPB in the same exact configuration and it worked perfectly. So, there was something (and not noise), maybe a signal sucker (although there was nothing identifiable to do that) that prevented x-10 from working but UPB worked despite that. So, in that regard, their advertising is accurate, UPB is more reliable than some other technologies.
Now, here's the rub, and the crux of the situation imho and why you are so frustrated and wanting to blame (even though you say you aren't) the manufacturers. It's what they
don't tell you that is killing you. They don't say that all of the above is true until you have severe noise or something else that compromises the powerline, then we don't work just like anyone else. That's the part that we are trying to get across. I am not an EE so I'm not going to pretend to explain the why's or why nots. I don't know what a power company looks for as far as 'clean' power, I doubt too much. I think all they really care about is if you get steady power to your place and stuff works. I don't think you can compare a typical consumer electrical product running to a special signal piggybacking on the power line. You are right in some of your points, the powerline was not designed for these signals.
But here is where we digress and sorry, but I (and many others) think you are wrong and misplacing your disappointment.
4. If someone decides to design and provide a new product that uses the existing powerlines as their transmission media, the onus is on them to ensure that their product works on the platform they chose to piggyback on.
That's true, but the disclaimer should be 'typical, not infected with noise powerlines' I agree that ALL manufacturers that make these products should add a disclaimer that outside influence of noise can render the system unreliable. But they need to be careful, it doesn't break or make their device useless, it will just sever communication and make the 'system' not work. Remove the outside interference and it will work as designed.
Since it's easy to mix in the power company and their lines, let's take another example, a point I tried to make earlier, that shows we are not trying to blame the power company or their lines or service, although it very well could be. Let's take a look at wirleless. Let's use an example from earlier which apparently didn't make any impact. So lets say we have a tower built and setup by American Tower Company. That tower is designed to broadcast wireless tv signals over the air where it is received by say a Radio Shack antenna. Both American and Radio Shack designed their products to transmit and receive signals respectively and say they even claim their stuff is 99.9% reliable. So you live in this nice house 35 miles from Americans tower and you sit in your family room where the Radio Shack antenna picks up the signal transmitted by Americans tower and feeds it into your nice Samsung tv and there you sit happy as can be with this beautiful picture. This goes on for years and you are extremely happy. Even you would agree American and Radio Shack are 99.9% reliable because you have never even seen a hiccup in your beautiful tv picture. And the transmission media, the AIR, is perfect. Now, big bad XYZ company comes along and builds a 15 story building a few miles from your house. So there you are watching this same beautiful setup you've enjoyed, but now, alas, the picture is garbage - it is pixelating like crazy. OMG, what do we do? Do we blame American and say their claims are wrong and their towers don't work as advertised? Do we go after Radio Shack with the same claim? Do do we blame, I don't know, the planet because the air does not work any more? The answer is simple, the problem is a new source of interference that neither American, Radio Shack or anyone else would have known would be there but could certainly impact the transmission of the signal. So, what do you do? Well, you could look for the problem and identify it? Maybe you can, like in this case, but what if the problem was a huge flock of birds that just flew right by the tower occasionally which only sometimes impacted your picture? Or what if there were some weird atmospheric anomaly which bounced the signal around and also impacted your otherwise 99.9% reliable picture? Those would be tougher to identify, but certainly an issue.
Do you get the point? The same thing can happen with FRS radios, or guess what, even Rupp's ZWave switches. What happens if you have a house full of ZWave switches and they are working perfectly. You are happy, right? The mfg claims that the stuff is reliable is accurate, right? But now say you remodel and put up a new wall and it just so happens it was in the path of a switch that was not in a mesh, it only had the one path to another switch but you now weakened the signal with the new wall. Now half of your ZWave switches don't work any more. Who's fault is it? Did Leviton mess up and are their claims wrong now because you put a new wall up and broke the system?
The bottom line is manufacturers can't design to every possible unforeseen and outside influence. Sorry my friend, but nothing in this world is perfect and if you think it should be, you will have many more disappointments in life. I can guarantee you will have many more disappointments in HA.
Closing random thoughts - you mentioned
Finally, I firmly believe that if the manufacturers of this technology ever want to move from the realm of the hobbyists to mainstream
Well, I can tell you that UPB is used by literally thousands of professional installers that make their living off of it. Why? Because it is a quality product that typically is very reliable. It is definitely not just a hobbyist product.
So this is not about "fixing the blame", it's about "fixing the problem".
I agree, so go and figure out where the noise is coming from. And if you can't, hire a professional in this area (don't miread that as you are not a professional - I'm sure you are in your field of expertise). And if they can't then try another technology like wireless, but be cognizant of the fact IT CAN BREAK TOO! You are actually lucky in that you have this problem now before you install 8000 sq ft of it. Imagine how you feel if you installed 150 devices that worked perfectly THEN your noise started.
In my opinion, one of the root causes of this problem is that expecations for the reliability of UPB have been set too high in the manufacturers' marketing materials (I think Digger's post illustrates this nicely). Quality perception is all about how actual performance measures up against the expected performance. Although fixing this expectation issue will not help me with my problem now, hopefully it will prevent other from stepping into the same pile I did, and more importantly improve the quality perception of this technology.
Well, you are not the first to be sorely disappointed by marketing materials. And HA and electronics are not the only realms. I bet if we did a poll here, > 90% of respondents would say their actual performance
does measure up to their expected performance. The only 'fight' you have here is to urge manufacturers to put some sort of disclaimer about noise. But the only way you are going to know if it works is to try it. Any you do that as a hobbyist by reading the wealth of information here, then work with a 99.9% reliable (sorry) vendor like AO or others around here. You get a starter kit and see what happens, if there are issues you either buckle down and find them or return the stuff and try something else.
I'm sorry for your disappointment, really and truly. I am disappointed that I have UPB issues as well. But I only have myself to blame. But I was not smart enough to predict that my new electric cooktop would spit out 15-30 lesters of noise. I was not smart enough to predict that my Pentair Intelliflow pump would create 3-10 lesters of noise. And I guess SAI was not smart enough to design around that either. Oh, and that stupid Heath/Zenith motion light that does weird things to my signal. I wish I were smart enough to warn people to not waste all the time I did troubleshooting this stuff. I wish I was smart enough to tell them what to use so they wouldn't have problems or disappointment, but alas I am not, I can't predict what interference may come along and break their system, or prevent a new one from working. All we can do is urge people to use a hardwired system like we have here for years and then at least external interference would be eliminated. Perhaps one day a technology will come along that truly is perfect...
Now, lets go have a beer!