Well, I was in the same predicament not too long ago, with different devices, but still a switch from a BB to an Android device. So here were some of the things that have won me over to Android instead of BlackBerry. First, yes, BBM is cool, if your friend has a BB. If they switch devices, or you switch devices, or they don't ever have a BB to start with, its rather pointless. Gtalk on the Android serves as a pretty sweet replacement, and you would be surprised how many of your contacts already currently use it anyways, so no true loss there. Second, the gmail functionality of the Android is unmatched, even with the BIS 3.0 roll out that just took place. Never would I have thought that a mobile device could have so well replicated the experience that you are given on the web version. The physical keyboard, well there is not much to say there, thats a tough battle since its not something you can compare apples to apples. I do believe however you can use a bluetooth keyboard, or use the speech to text, and no typing is needed

As for the battery life, that is dependent on your usage habits obviously, but adding something as simple as could help your experience tremendously. Seidio makes amazing batteries and that could give the little extra life that you need in order to achieve what you want. You won't be able to match the marketplace of the Android on the BB, and also, you don't have to wait 5 minutes for your device to reboot everytime you do get an application update.
So I know the change can be a little tough at times, and you may always fear the "what if" but know that you are making a good choice with the Android, and many of the features will exceed what you ever expected. I converted, and honestly couldn't be happier.