I do recall one review in _Hi-Fi_News_and_Record_Review_ on an early laser turntable that wasn't that positive. The laser turntable was far noisier--the records needed to be cleaner than clean--and even when all was going well, the laser turntable sounded only as good as a regular turntable at a fraction of the price. (A pretty small fraction, too, if I recall right). I don't know about laser turnables since that time, though.
Then, one obvious disadvantage with laser turntables is that you can't play with different cartridges, power supplies, etc, etc, etc. (Maybe this isn't a disadvantage, after all....)