Does Mail (Mavericks) have an "intelligent" spam filter?

Yes, it can be trained.

If you're referring to the virus filtering in OS X Server, it is not trainable, but it does automatically download updates to the recognition database. The Junk filtering in the Mail client is trainable.

Yes, the Mail program installed on all Macs has Junk Mail filtering. You train it by using 'thumbs down' on messages and after a few weeks it has learned from your training.