The good folks at Kotaku (Mike Fahey specificially) just reviewed Riptide GP, and gave the game an emphatic thumbs-up, naming it their Gaming App of the Day:
I had no idea the sort of juice these Tegra 2-powered devices could pump out. The age of console-quality Android gaming is upon us, and Riptide GP is one hell of a good start.
Check out the full article here: Riptide GP Rips Android Gamers a Console Quality Racer