I like laughter tracks on studio sitcoms but find them jarring sometimes on other types comedy. Alan Partridge 1 & 2 in particular could really do without them.
I heard a really interesting piece on a podcast (This American Life I believe) that focussed on an incident surrounding an old studio sitcom called The Nanny, where the star had recieved death threats which led to the set being closed to a regular audience. Their solution was to approach an acting agency which selected the best laughers from their books to make up a 'fake' audience. They ended up doing such a good job that they became highly demanded and were let out to a whole host of sitcoms. In the end the agency tailored their service almost exclusively to productions requiring really good laugh tracks.