While it might be a wonderful product, everything eventually needs service. Kohler is a big pain in getting parts, and on some things, I've heard they've just told people, sorry, can't help. They tend to change their designs on a whim, and their parts book is more like a telephone book, so few people carry the parts - so you are stuck with special order from the factory.
There are a bunch of 'systems' out there. Personally, I've had good luck with Grohe www.groheamerica.com, but many of the pro's prefer stuff from Delta. I'd stick with a company that doesn't change the guts of things with every new model - most of the US manufacturers and some of the European ones would qualify. When they use the same guts for awhile, you have a much better chance of finding parts locally when you need them. On some, the same valve might fit a dozen or more trims, which makes it cheaper to produce as well.
Connecting all of the bits can be daunting, but doable if you go with pick and choose configurations.