I enjoyed it.
The twist of the lizard having been bitten by a human, not wanting to be in human form was excellent. His character was very humorous, I thought, especially, as Arksided mentioned, in the graveyard.
I didn't recognize the actor playing the lizard, but he sounded English. Rhys Darby, so maybe he's Welsh? Apparently he was in 'Flight of the Conchords', but I've never seen it.
Also, the sight of the lizard witnessing a human attacking and savaging other humans was amusing. It was obvious to the lizard that he would be blamed for the attacks.
Did nobody else think that the old man, a 'peeping Tom', looking through the stuffed head on the wall, was funny? Especially when the lizard pulled the head off the wall to reveal the old man, screaming!
The TV Times have it as 'Pick of the Day'. As they say, "...This enjoyably silly story has its tongue firmly in its cheek as it follows our heroes chasing down the perpetrator of several grisly murders...Lots of fun, 'Mulder and Scully Meet the Were-Monster' is by far the best episode so far in this six-part X Files revival."