Agreed -- I just ran a non-scientific test for you, as I was curious myself.
Server A: SquirrelMail 1.4.5, Courier-IMAP 3.0.8, NIS+ lookups and NFS mounts to /home, Maildir (existing production, rock solid)
Time to open my mailbox: 36 seconds (*)
Server B: SquirrelMail 1.4.9 (in Courier config), Dovecot 1.0rc22 (Courier namespace mode), PAM/nss_ldap lookups with same NFS mounts (new beta server)
Time to open my mailbox: 4 seconds
wow...
Obviously there's a million factors (distro release, CPUs, memory, load, etc.) but across the board my beta users see astounding performance gains. Doing searches inside Thunderbird on random strings exhibits the same behaviour, what used to take a minute takes 2-3 seconds now.
Stop it! I was up all last night getting my server ready (upgraded to gcc 4.1.1 from 3.4.6, which, of course, meant I had to rebuild the entire box, which only took about 7 hours)...
<sigh>
Now I'm gonna have to find the time to just go ahead and do the migration... we experience the same slowness (courier-imap 4.0.4/maildir) with both squirelmail and tbird, to the point that searching on large folders (1+GB w/ 7k+messages) often will just timeout...
I think I'm actually salivating... lol
--
Best regards,
Charles