I have the same experience (I get my GMail on my phone before I do on the webclient).
What does that do for battery life? I know I have to keep my email checking on a schedule on my Centro, because it just zaps the battery if I let it push emails. I have both my GMail and my work account on it, so I get quite a bit of email--maybe 100 a day. On a busy day, my battery gets absolutely killed because of the constant pushing. So, I've throttled it back to only check every hour or so.
My battery life is excellent. If all I did was have it push email all day (and GMail chats), the battery would last a good 2 - 3 days before going kaput. And then of course on the Droid OS you can kill applications that are running in parallel if you don't want them eating up your battery (using a free app). This helps extend the battery life as well.
Thank you.
