... if you use a system that has centralized dimmers with low voltage switches in the wall you are forever stuck with that type of system. On the other hand if you go with a system that puts the HA supported dimmers in the same wall locations as you would "normal" switches - a future owner can always put "normal" switches back in if desired.
But again that's for lighting because it's such a core component to the operation of the house. I think in everything else, the generally accepted theory is to wire the hell out of the house so you have unlimited options. If you want a regular thermostat that's not automated, just swap it out and don't use the cat5 you left there - who cares?
For security, there's just no comparison to wired vs. wireless - cost is a fraction for wired while the walls are down and the performance is way better. Along that note, think about wiring for water detectors around plumbing fixtures, extra motion sensors if you want fancy automation, etc. This is where you'll probably forget to wire something. For thermostats, sprinklers, everything else - just run the necessary wire so you can put controlled versions of the controllers there. Also since you can, you should probably consider a water shutoff device (Elk's water shutoff or a WaterCop).
Video is the same - wireless video is generally less secure and more expensive. If you can wire analog cameras and spend the money or the DVR or controller IMO that's a better option.
Speaking of sprinklers - what I did was run a Cat5 to the garage and put an output expander and relay board there (Elk M1RB and M1XOVR) inside a can where the sprinkler controller would normally be located - gives you lots of options in the garage having the databus extended there... and when I move out I just go buy a sprinkler controller and put that there in it's place.
I personally steered clear of the Elan's and Control4's specifically because you can't DIY - and a couple years ago, HAI didn't even like DIY... but I absolutely love the look of Elan and Control4's touchscreens and interfaces. Maybe you can DIY the Elk, UPB, thermostats, etc - and hire someone to just come in and place the controller and do the integration? If you get a good dealer they should see that you're capable and work with you - if not, they're the wrong dealer for you.
