They hold a Shad Festival each year on the last full weekend in April. It is crowded, driving through town is awlful and parking is worse. We have attended the festival many times and had the best times when we took the train in from Ringoes (no longer running)or used one of the satelite parking areas they arrange for the festival. The festival is worth a visit unless you dislike crowds.
Unique Suggestions: Don't try to park in town.
The town is a tourist trap-it is designed to suck tourists in and keep them there. But it doesn't prevent it from being a nice place to visit. I wouldn't recommend actually buying anything in the shops unless you're wealthy because you can get the same crap for much less in a regular shop somewhere else.