We were out there in late August '09 and stayed at Hadley's Point Campground. It has a variety of sites, from wooded to open. It was fairly quiet, the pool area was decent, reasonably priced, and the sites were fairly sized depending upon where you are in the park. We were in a wooded site that was a bit tight. We spent most of our time out and about sightseeing.
Here is the RV Park Reviews.com for Bar Harbor.
http://www.rvparkreviews.com/regions/maine/bar-harbor