I'm not quite as sold on the whole-house systems. A co-worker had one of those installed. It always seemed suspicious to me because it literally was sold to them by a door-to-door salesman toting around water samples. Big-time scare tactics. It was one of those multi-thousand-dollar, reverse-osmosis, whole-house setups. While it did make their water taste better than 'tap', it didn't seem any better (taste-wise) than what was coming out of our $100 system. Nice to have filtered water at every tap, I guess, but it sure seemed like a waste to spend that much money for that super-water, only to literally just flush it down the toilet.
My old place had a whole-house system because the source was a well. It was a traditional softener with a carbon cylinder filter added, along with a couple of pleated paper filters. The softener wasn't entirely necessary, but the carbon filter did a great job of soaking up HS from the groundwater, and helped with stains in the tubs too.
An RO whole-house system would be massively expensive if it had enough capacity -- one of the things about RO membranes is that the rate of flow through the membrane isn't all that high, and I imagine a whole-house RO setup would have a storage tank after the membrane that would refill overnight.
