We spent 6 nights here from July 29-Aug 3. The park itself is beautiful with sweeping views of Seneca Lake. We stayed in Loop 5 which was the closest to the water. We had some trouble backing our 5th wheel in because of low hanging branches. But the park personnel were very helpful about removing some branches to help us. Recommend you book site 222 if you actually want a view of the water. There's a gap in the trees at this site that lets you see the lake and sunset. At our site (234) you just had to walk down a small hill to be lakeside. Very scenic, and pretty private. I swam every morning, and felt like I had the lake to myself. Sampson is a good jumping off point to tour the wineries, Watkins Glen, etc. But make sure you have all your supplies - the convenience store in the park is a joke and there are no stores close by.
There's also a marina in the park - but no facilities such as kayak or jetski rental - a little disappointing.
Overall I would recommend this campground