I'm really excited about Gmail+IMAP. I'm at a cafe with much higher bandwidth than the signal I usually steal from my apartment, downloading my Gmail archive for "offline use." I've always been slightly perturbed that I don't have my own permanent archive of my e-mail; I don't think Gmail is ever going to vanish, but...you never know. And it's nice to be somewhere without online access and be able to browse old e-mails.
Ever since the fall of my junior year of college I've been archiving (mostly) everything. For a long time this was some Pine, some Outlook POP, some Thunderbird POP, some (other) Pine...but I finally unified everything into three or four fake servers within Thunderbird. It's a little buggy sometimes (the dreaded 12/13/1969 header fuckups) but it's nice to be able to find everything under the same standard. And now my Gmail is under that aegis (although I'll still use the web interface 99% of the time).
What's even cooler is that I can contemplate integrating all this old e-mail into my G-mail IMAP server, so that I really can finally say I have everything in one place from 1996 on: work, school, and personal. My initial attempts at this haven't really worked, though, as Gmail (web) isn't really recognizing that a sent-mail from 1996 put into the IMAP Gmail-sent folder corresponds to being in the Sent Mail label on the web. It's also not recognizing the old date and putting today's date on it.
Oh well. It's a step.