Yes, it covers two PCs. I use it at work and at home with no problems. As for it's features, just make sure it's setup correctly (meaning it's automatically checking the right inbox and whatnot) and it should by default filter out most spam. Then, if you do happen to get spam in your inbox, you can report it so that you help everyone else too.
yeah, I think I had it setup correctly. It did give me an error though, something about encryption with OE...I didn't know I had it on that setting nor did I take time to figure out what the solution was. I'm liking the networked idea more and more though. That is akin to being able to block domains I think - not akin but perhaps comparable.