Last night I stumbled across sup. I've been a long user of pine. (Yes, I know about the politics behind "free or not" license, and I tried to migrate to mutt - alas. Mutt was too slow for me in managing a lot of folders over imap).
But something like a gmail for my mails... awesome. I grabbed a git version of it, and below go my impressions of the first messing with it during the weekend.
1) don't use the sup-config to add the sources.
use sup-add directly. Though you can use sup-config to generate the command lines, in case you can't read the --help output of sup-add.
2) run sup-update before the first use!
I tend to store a fair amount of mail - with the total size of mails that are accessible at one point in time being about 1-2 Gigabytes. I tried to let the sup itself index it - terribly bad idea! It seems like thread addition becomes slower and slower as the number of threads grows - so after about 800 threads I gave up. There were also a couple of odd unreproducible crashes when I tried to navigate the list of the mails while it was being indexed.
3) ssh+mbox code seems to be slightly out of date - at least it did not work for me.
There's not a big deal to patch there - pretty much all the changes are in unsafe_connect and do_remote. I've hacked the things really not very cleanly, so no diffs. But if you are a beta user, this should be trivial to you :-)
4) password storage in the config file
This is totally not awesome, but easily fixable - e.g. by interfacing with the pinentry executables.
5) the zillion of folders that I had before are not so much convenient to poll.
Under the presumption that I'm going to use the gmail-like approach, I've simplified the procmail filtering, leaving the "to-me" folder (which gets into inbox), "critical mails" - which also get into inbox with other label - and "bulk" folder (which gets archived immediately and labeled "bulk").
Overall the search looks to be reasonably fast - although I only have about 20000 messages, which is not a big amount. We will see how it behaves in a year :-) - and most importantly, during he working week.
Update: I found that a few of the mails - seemingly the bigger ones were dropped by some destination system. Interesting. I am curious why.
Update2: well, at least one of them was me fatfingering in the middle of the night. The other one still unknown, but when I resent today, it worked. odd.