I've been trying to figure out a way to get IMAP setup on Treo 680 (without having to pay for a third party application). Since the default VersaMail email program version 3.55 doesn't play well with Gmail IMAP (only POP3), I started to do some research. Thankfully, I stumbled across this thread which lead me to this brilliant blog entry with step by step instruction which showed me how to obtain an updated VersaMail 4.01 that was intended for the Sprint Palm Centro users. I'll save the rant on why Palm chooses to single out Treo (Garnet 5.9.4 users) when it is the exact same OS as the Centro for next time.
In short, you can just point your Blazer browser to this .PRC link or go through the steps recommended on Palm's Centro support page.
GMAIL IMAP settings can be found here
Update 7/21/08: I have been using VersaMail 4.01 for the past two days and have a very satisfied smile on my face as its working out great. IMAP support is a must have for smartphones. Don't know why Palm would not provide this as an update for Treo 680 users.