I like the interface of 8 but I don't like the link scanner and as a result of turning it off I have this little exclamation mark sitting next to my clock all the time. I find it slows down my internet speed just enough to be noticeable.
I could never get 8 to update properly, so I started using Antivir again.
personally, i think that avast! is the best. it detects things AVG and others dont.