We visited the Sandbar three times while staying in Praa Sands. The food was first class on all occasions but there were a few down sides.
The place has seen better days and would benefit greatly from a complete clean-up/refurb. Food prices were a little steep, but the drinks were really expensive. I suppose that's what you get from being the only place for miles around.
It depended which staff were on duty as to how friendly they are. I always base my tip as a per-centage of the bill depending on the service and it varied for all three occasions.
Having said all that (and if you can put up with the dogs, the occasional surly staff member etc, this is a good place to eat with stunning views across the bay.
(Problems with ratings box again. I give it 3 for service, 5 for food, and 4 for value)