I have used PMail for like 10 years.  I hadn't heard of The Bat!, so I read the review on this site.  As I was reading, I kept thinking, "Yeah, so, PMail does that, too."  I use multiple accounts/identities, have a boatload of filters, folders, subfolders, multiple address books, distribution lists, and customized spell checker.  I love it. The list of features is long and rich:
http://www.pmail.com/overviews/ovw_winpmail.htm  :-*