It should perform as well as the other eco-Totos. It's my understanding that they actually dump the same amount of water, but they've more carefully calibrated the refill so it doesn't overfill quite as much. Pretty much all toilets put more water than will stay in the bowl during refill...it just continues to overflow and go down the drain. If you carefully adjust, it stops when both the tank and the bowl are just filled. I also heard that if you don't like it, you can change the fill valve, and it reverts back to the 1.6gallon flush.
The only things normally needed for maintenance on those toilets are the repair cap gasket (available at Lowes) and the flapper valve (also available at Lowes). Both are quick and easy to replace.