I don't know about the G1 personally, but I really like the battery life on the BlackBerry. I use it much more than I did with my older phone, and it still lasts twice as long as it did before needing to charge again. If your someone who likes to type often you may get frustrated with the touchscreen typing, at least I know I do. I like the tactile feel of the keyboard.
Apps can be a bit costly, but I always finds the one I need. Gaming is just fine for what I do (I like tower defense type games), but it may be better on the G1 if it has an accelerometer.
I have the 8520 and I enjoy it.
I come in last, but just in time for breakfast.
Keep it through, Keep it through, forever blue.