Why wouldn't anyone want one is a mystery to me considering that you save somewhere in the neighborhood of 1000 gallons per year per person of water.
Dual flush is big all over europe/asia/australia etc for 5-10 years now.
For a variety of reasons it didn't catch on here until Now. The Aquia is toilet that will change that imo.
It can take twice as long to install. Especially if your plumber never installed one before. no biggie.