I'd say Mike's got it pretty well summed up. I'd only stop to fish Hingham if I were driving by and saw fish breaking right now. Most of the fish in the area have started their run to the south. Yes, there are still fish in the Boston area, but locating them is a hit or miss proposition. If you've got the time, I'd strongly recommend reading either Peter Jenkins or Dave Peros's column and going to one of their suggestions on the cape or in Rhode Island.
I did fish Hingham last week the night after a trusted fishing buddy witnessed an awesome blitz. For my trouble, I saw one swirl. I would have been much better off to have headed down to the canal or to someplace on the cape.
As far as fly fishing, there's a number of great spots to do it. You might want to take a look at the list of spots someone posted on the rec.outdoors.fishing.fly newsgroup last night. Worlds End is excellent and the bathing beach has it's times. Unfortunately, the time for the bathing beach won't come again until Memorial Day. You'd be better served driving further to the south.