Hi, my name is Micah and I am unhappy with Z-Wave.
Like IVB said, most of my bitching, moaning and complaining is done over at Cocoontech.com but it can be summed up pretty nicely.
While the Z-Wave technology is awesome and I'm really happy with the number of manufacturers and the direction it's going (in terms of the wide range of devices) the interplay between different manufacturers is atrocious.
My biggest road block/complaint/pet peeve/etc. is that you have to ensure you either buy hardware from a single source or you have to try to muddle through all the manuals to find out if the remote from one manufacturer will support all the hardware you want to use.
For example, while the Intermatic controller can add a Z-Wave thermostat to the network, it can not control the thermostat. Additionally, the HomePro controller can control a single thermostat but you can't use the timer feature on the controller to change the thermostat set point.
If all you're doing is lighting, you shouldn't have any trouble. If you want to expand what you're controlling (thermostat, sirius satellite receiver, garage door opener, window shades, etc.) there's no guarantee and no easy way to find what devices will work with which controllers and even if they do "work" with those controllers, if they'll work they way you want (or expect) them to.
In summation: Lighting only, go wild. Expanding beyond lighting? Hope, pray and be prepared to return hardware when it doesn't do what you expect.