I am one of those who is quite happy with his AOL account. No SPAM (well, about 4 a day), it just works, all the time, everywhere.
Nicely integrates with Mail, iChat, Address Book, and Safari via AOL's
Service Assistant (5 star rating on VersionTracker)
A Universal version is in Beta. That too is getting a good rating (4.8 stars vs the 3.1 for the current version).
Like all email clients, it has its shortfalls.
BTW I: AOL is now free, as in nada, zip, zilch (as long as you are not on dial up).
BTW II: AOL Radio (200+ XM stations) is also free.