With one of the new Android releases coming up in October lets go over differences. Android 2.3 is being nicknamed Gingerbread by press but as you know according to Google/OHA 2.3 is not Gingerbread as there is never a full transfer of all the changes in the private Gingerbread tree to any public release.
So what is in Android 2.3? Expanded cloud messaging and voice recognition. More video codec support along with WebM. Bluetooth voice commands. A complete UI refresh that might prevent all the OEM adding UI skins which has been delaying new releases being sent out to device owners. Last but not least, a possible USB api update to include apis for applications to interface with new USB features in preparation of OEMs supplying full AB USB port modules.
Wait! Part of the cloud message update involves a promise that Google gave back in May, Music store by year end holidays. That is why if you had viewed the android kernel commits recently you saw some drm commits.
So what is Android 3.0? Same as above in that although the press has labeled is as Honeycomb, the private tree never gets a full release or folded in to a public release. Its easier to just think of it as Android 3.0. As Google has talked to OEMs and noted the tablet trend it has come up that OEMs are preferring Android than Chrome for tablets.
Using Android for tablets presents some new challenges both in what constitutes an Android device as far as expected hardware inputs, outputs, ports, screen sizes, etc. Thus, android 3.0 is being developed to address these challenges.
But, there is more! Remember the Web APIs demoed in May(IO video)? That is part of what is in Android 3.0. And of course the improvements to support GoogleTV.