I switched from Entourage quite a while ago largely because it did virtually nothing to trap spam despite my use of various bolt-on filters. I find that the spam filter in Apple's Mail is excellent. I can't remember the last time it mistook a valid message for spam and actual spam is identified very accurately. Switching to Apple's mail had three benefits:
1) It works.
2) it's free.
3) it gets one more piece of Microsoft software liability off my system.