There’s no word yet on the official schedule or road map for IMAP support in Gmail. Google appears to be doing a silent rollout of this feature. Some users already have it, but others don’t.
You can check if your account is IMAP-enabled by looking under the “Settings” link to see if your “Forwarding and POP” option is now “Forwarding and POP/IMAP.” If your account is IMAP-enabled, these instructions will help you get configured.
The tricky part here is that Gmail doesn’t have proper folders. Google got around this by using labels to indicate the folder that a particular mail is in. Google’s IMAP behavior chart lists the details.
According to CNET News.com, Gmail’s new IMAP features is strictly catered to client-side access only:
Also, it’s worth noting that the IMAP support is one-way: You can use IMAP clients to read and send your Gmail. You cannot use the Gmail interface to access e-mail from non-Google IMAP servers or from Exchange. The only non-Google e-mail servers that Gmail can access are POP machines, and you don’t get any mailbox synchronization with that method.
Will IMAP support in Gmail be of any use to you?