The new UI is always an issue, but it's a minor one. Every six months or so, I try all the different IMAP clients to see if there's anything better than Mozilla (and, so far, I always end up back with Mozilla). Figuring out how some new thing works isn't that bad, particularly if the software was well designed.

No, the real issue for me is simply having all the required functionality and having it all genuinely work. Switching MS Office on Win2000 to MS Office on OS X won't be a big deal. I'll probably keep running Mozilla as my e-mail client, although I'll play with Entourage. The only real thorn in my side is synchronizing to my damn cel phone.