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The version currently available in the Android Market is actually Angry Birds Lite (a free trial with several of the chapters locked) and it's in beta testing, so it's not quite bug-free on all Android devices. In fact, CNET reports that it doesn't work at all on Evo handsets.
The comparatively bug-free full version is coming soon, but in the meantime the Android users who own devices that can run the game can see what iPhone and iPad users have been going crazy about.