Around 1 month ago I said I had made the switch from KMail to Thunderbird for managing e-mail. Well, now I must confess I am making another switch, this time to Evolution, the native e-mail client for GNOME.
The main (sole) reason is that Icedove (Thunderbird) was unreasonably slow lately. Maybe it's a matter of versions (I'm running the latest in Debian Lenny), but it was driving me crazy. And so is Iceweasel (Firefox), but that's another story. Evolution seems to be as fast as KMail to start up/minimize/maximize/quit, and as fast as Icedove to manage the IMAP folders (something KMail was seriously lacking).