i've been using mutt as my mua for over 8 years now. long ago i would ssh to my server and run it on local maildirs, but as soon as i started using smartphones and multiple computers i had to switch to an imap+ssl setup. mutt's
header_cache option has long made accessing large mailboxes snappy, and the recent
message_cachedir option available in 1.5 makes browsing through messages with attachments equally snappy over imap.
a useful side effect of message body caching is that it provides an offline copy of entire mailboxes which get synchronized automatically and can easily be read in mutt as a local mailbox... well, almost.