I'm seeing some odd behavior on Android...running 2.2 on HTC Incredible.
I have an IMAP account configured through the built in "Mail" program. First of all, when you send messages from this program, it copies them to a local "Sent" folder, and there is no way to specify a remote IMAP folder for this (e.g. "INBOX.Sent"). So then, I try to move messages manually between the local "Sent" and the IMAP "INBOX.Sent" folder, and it appears to work fine, but when I check from another IMAP client (e.g. Thunderbird), I don't see the messages in "INBOX.Sent".
Has anyone else run into this? Any idea how to resolve?