Supcase's version looks nice (if you don't mind the G-Shock type of look for your watch), isn't too bulky and allows good access to the crown. It doesn't cover the screen, but protects it by having a raised surface all around it. I've had one on my watch for about three weeks, no complaints whatsoever.
Cases are fine, as long as they don't cover the face. I say this only as a warning because I used a plastic cover from Amazon that covered the face and a bit of sand or something got under it and scratched part of the coating on the screen.