Funny... we're so used to NOT having the "My Tanks" thing there, we're not used to using it again!
You're probably at the borderline of where people start considering skimmers. I'd say that if your water quality is good without running one, then you probably don't need one. If you end up going with corals someday, you might reconsider. Skimmers won't kill off the things you mentioned... I run one and have had no problem with snails reproducing, massive coralline growth, etc.
thing, as melosu mentioned, is a debatable thing. I've never run one so can't really comment.