Mobile Team has released an update to the ArcGIS for Android App v1.0.1 and is now available from the Android market! v1.0.1 includes support for devices with ARMv6 processors and running Android OS v2.2+. For more information, read the Blog topic http://bit.ly/vsT1pB.
If mapview has wrap around enabled, then once you tap on a graphic, a callout sometimes shows on the other instance of the graphic - the instance that can be revealed by scrolling the map around.
For example I have a graphic placed in north america. I zoom out all the way and tap on the graphic. At first look it appears that callout did not work - there is no callout where I tapped. But if you scroll the map, it will wrap around and north america becomes visible again - this instance shows your popup.