He was the least talented actor in the film. It was obvious he didn't really know how to ''act''. The other actors were more on the ball. Jon was playing a degree of himself as he's also fairly ''awkward'' in real life based on the interviews at that time.
shareI'm not sure about his talent, as the only other movie of his I felt compelled to watch was Blades of Glory, but I did notice that he seemed to drop off the map.
Looking at his IMDB I do see now that he has continued to work, but it mostly looks like random episodes of TV shows, some voice work and the occasional small part in movies no one's heard of. His day day in the sun was brief, only lasting about three years and three movies (Napoleon Dynamite, Benchwarmers, Blades of Glory), and then it was back into obscurity.
I thought he did fine in Blades of Glory and that film seems to have done well enough financially, so I'm surprised he didn't get one more shot at a big movie after its release.