That's an informative post dishe and I want to add a battery related footnote. By using
nogprs and configuring all my POP3 accounts not to automatically check for emails, I have doubled my battery life. It's a huge sacrifice and ridiculous since it's the phone's most important feature, but the battery on this phone sucks so much that no auto email is better than a dead phone by noon.
I don't personally use Direct Push with an Exchange server, but if anyone can provide a battery consumption comparison vs POP3 automatic checking it would be appreciated.