It seems to be pretty good, but I haven't had Zone Alarm Pro installed for long, so I'm not absolutely sure. The scans seem to be very quick and it does find stuff to delete (marked low, medium or high risk), but I still have Adware SE installed on here just in case.
Though, I find Zone Alarm Pro slow to load and a little over sensitive for my liking. I had to go into Safe Mode the other day to completely delete the IM Security stuff, as even when you turn it "Off", it's still on. In MSN Messenger, it wouldn't show display pictures, voice clips, let me send files properly or let me see emoticons. At least they all work now...