Version 6.5 here but ... actually apart from the user interface (which sucks), I like the functionality of Lotus Notes.

I can easily work on my e-mails from home, the office or on my work laptop with everything synchronised; easily replicate to my laptop (useful for when I have no Internet connectivitiy); etc. Impossible to do with POP3 and not so functional with IMAP (AFAIK) (although I don't know about MS Exchange/whatever).