I like it, actually the Amazon App store and AB Rio.
Rio is more different from the original than Seasons. Instead of trying to kill pigs you're trying to free caged up birds. The game play is still the same though. I only played a little over lunch but the backgrounds seem more interesting and the game played very well with a few new touches to animations and the interface. A coworker who played a little more than me showed me how in some other levels things like ceiling lamps can get in the way of your shot, changing the game a bit.
I definitely think it's worth installing the Amazon App Store for it and I actually like their app store. I like the way you can view two columns instead of just one at a time. Besides that I don't see a lot of difference. It does seem to have video as well as screen shots. I also like the way it displays the screen shots, letting you slide through them left to right.
Did we need another App Store? Probably not but I'm all for competition and I do like Amazon