For me e-mail still works. With SPAM filters getting better and better I've never quite understood, why people insist on e-mail being broken just because of SPAM. Generally UCE/UBE mails hardly reach my inbox at all these days. Of course there a kind of wave pattern with spammers finding new tricks and filters needing some time to catch on but IMHO it isn't that bad.
By the way, I think the Google Trends search was a bit "unfair". It seldom happens that people explicitly use the term "IMAP4", in my impression it's just "IMAP" mostly. In that regard the search for "pop3, imap -substrate" leads to somewhat less dramatic results. POP3 still comes out ahead, though ... ;-)
Still, for me there's no going back to POP. I just leads to trouble with switching mail clients and endless trouble if you want/need access from more than one machine.
Gmail is tempting me time and time again for it's the only alternative to the IMAP/mail-client combination I see right now, but just like you wrote in the Hawk Wings mail client interview a couple of month back, I simply cannot bring myself to trust Google ... Which is a shame because it probably is the only mail client that, well, "borrowed" from the old Mutt motto, sucks a little less than all others right now, GUI clients inclusive.
As for Apple Mail I kinda agree with what Ashish Gulhati wrote ( http://netropolis.org/hash/blog.cgi/Tech/Email/thunderbird_vs_apple_mail.html ).