FWIW when I tried to use x10 I had very similar issues, I could not even make it work on the same circuit, with everything unplugged, including removing hard wired fan controllers, etc. I got so frustrated I have up and evaluated UPB and Insteon and went with UPB. For the most part it has worked great, but yes, you can still have noise or phase issues but they are usually very easily rectified with UPB. Don't be fooled into thinking Zwave will be problem free. Sure, it works great for many and may for you as well, but you potentially can have same/similar issues. Instead of powerline issues/noise, etc you simply get wireless interference, signal blocking, etc. Bottom line is any technology is going to have its issues. For me I choose not to use wireless for several reasons. One thing to is at least with powerline, you can measure things easily and narrow down to apply fixes. I'm not too familiar with Zwave but I'm sure its not as easy to see what potential noise or interference there is 'in the air'. Maybe there are ways, but not as easy or cheap (free) like with using UPStart. But if you have time, try both and then invest in the one you are confortable with.