I wish people would stop saying Thunderbird 2.0 has Gmail integration. It doesn't. It has an option, when adding an account to say this account is a Gmail account. When you do that, you just have to enter your username and password. This is a glorified shortcut. You choose 'Gmail account' and it sets incoming server to pop.gmail.com and outgoing server to smtp.gmail.com. That's it. What's worse is that people keep saying Thunderbird 2.0 has 'Gmail style tagging'. Normally this wouldn't be so bad, but bundled with 'Gmail integration' leads you down a path of lies and deceit. What does someone think when they here 'Gmail integration'? At the very minimum, they want their labels downloaded along with their emails. They want to be able to tag something in Thunderbird and have it be labeled in Gmail next time they sign in. For the record, mozilla doesn't even call it 'Gmail integration'. They just say it is easier access to webmail, probably because that's what it is:

Easy Access to Popular Web Mail Services

Thunderbird 2 makes it even easier to integrate and use various Web mail accounts from one inbox. Gmail and .Mac users can access their accounts in Thunderbird by simply providing their user names and passwords.