My minimalist gmail interface is called "pine", which I believe is still considered to be the reference IMAP client implementation. If I were have to make this decision today, I might use something more powerful and extensible like "mutt", but for me pine is just fine.

I started using it again a year back or so when Mail.app became too slow for me to use on some giant mailboxes I have. Deleting 5k messages from an IMAP folder in pine takes maybe 5-10 seconds. Try doing that in Mail.app. I found my email productivity went way up after switching, so I ended up using it exclusively, despite the ribbing my co-workers give me for using prehistoric email tools.