a) I can't seem to get plaintext messages to display in a fixedwidth font. ETA: OK, this is fixed by a FireFox plugin called "Better GMail". I haven't figured out yet how many other things it can fix.
b) I can't get it to display with older messages at the top. I hate "newest first" sort. It's wrong.
c) When you archive or delete a message, it goes back to the inbox, instead of the next message. (This is a customizable behavior in Pine.)
d) I can't open multiple messages in new tabs; middle click (or command-click, on Mac) on a subject fails to do what it should obviously do (since clicking on a subject opens the message). This is something I can do even in my ISP's crummy low-grade webmail client, which I tolerate if I'm someplace where I can get a browser but not a telnet or ssh client.
e) I can't filter on an arbitrary header. Dumb, dumb, dumb. This means I can't look for "moodlepost" in the "Message-Id" header, in order to separate the mailings that are formatted to look like a one-to-one message from the poster to me, but are actually being generated by the school's BBS. I'll have to figure out something else that distinguishes those posts. Subject line is no good, because if you start an email conversation off of a moodlepost, then you do have actual personal email with the same subject...
I may add to this list as I go along... I have mixed feelings about its keyboard shortcuts; they're good in theory, but they also interfere with the Firefox "search in the current page by typing" system.
Oh, and the reason I'm using GMail is because Presidio has its email accounts hosted on GMail.