I really want to get into one, but I feel on the whole I've been let down by some slightly amateurish games that lack some polish.

I feel that if a larger publisher got into this (a little like SOE's foray into Free Realms) but allowed the assets to be opened up to the community, that the content would get very sizable quickly (much like secondlife and metaplace), as a result the quality does tend to take a nosedive so maybe it's better to manage all the content in that respect.

Runescape is a nice concept, I just don't feel it's such a great game, I'll definitely check out Sherwood, so thanks for the heads up.