It depends. Some things, such as the Tower of London, are must-sees. We were there last April, though, and found the lines so long and the food service so slow and overpriced we'll probably never go back. Once is enough. Sometimes touristy is comfortable, too- like the restuarant we went to in Rome twice on the same trip. The musicians played the same hackneyed Italian "touristy" favorites (Funiculi Funicula, etc.) both nights, but the food was good and the service was cheerful.

We balance the well-trodden places with place names that make people go, "huh?", such as our upcoming trip to the Orkneys.