Do you live in an urban or suburban location? My biggest issues with Z-wave are that it is 2.4 GHz, that it only supports 232 devices and that they will not support open source development. For a home control system, I want a small system with no spinning storage. I personally would never use Windows for a control application.
In one of my locations, I already have over 100 switches and wall warts. I also have 20 Logitech 890 Z-Wave remotes (I have had many problems with these so far, but I am not yet blaming them on Z-Wave) putting one in each room. Were I too add motion and temperature sensors, door sensors, ventilation controls, and window/shade controls, I worry about hitting device limits.
At my house in FL, I have 5 acres, so I am not worried about 2.4GHz, but in other more densely populated areas, I am concerned about problems with interference with the other million 2.4GHz devices out there. There are already problems cropping up in places like NYC, Chicago and San Francisco with WiFi networks stomping on each other. Adding more devices to this mix seems like a bad idea.
/carmi