If you’re a happy GeoServer 1.7.x user, then seriously consider upgrading to GeoServer 2.0. It’s a lot faster, its menu structure is a lot better, the UI is much improved (with a touch of Ajax here and there). I found some minor issues (which I’m looking into before raising my voice), but nothing that should keep you from updating.
I run GeoServer in Oracle’s OC4J 10gR2 (the standalone development version), and it runs without any problems. Since the OC4J is declared dead, I will be looking into deploying it to Weblogic, but that’s a completely different monster to conquer…