I think it depend on the caliber of restaurant you are in, if the salad bar is appetizing and clean.
Some of the huge mass marketed places with salad bars are just gross. We frequent some Amish restaurants, that are very busy and very well attended, and the bars are clean, restocked within minutes because they are so busy, have a little different clients and staff working, so I don't question the cleanliness or the quality of the food.
Anyone in Ohio, I recommend the Amish Door restaurant (especially the one in Wilmont) for a good and fresh basic salad bar. Lots of fresh whole produce, and some really different prepared salads that you don't see other places. Even includes the best ham salad I've ever eaten, and a great pudding type dessert (and a few others). Very clean, well stocked and fresh.