Well, he occasionally has this weird thing where he just forgets how to do customer service - like, people receiving broken gimmicks being ignored or dismissed, responding with a fake name (I think Scott?), etc. Not as bad as Outlaw Effects but enough to earn a reputation. Also he tends to re-release the same thing over and over, or put out things that aren't really worked out for real world practicality.
Personally I have next to no opinion of him, other than he seems to have a very high opinion of himself. It seems pretty extreme to have a community geared towards hating him, to me. That's a lot of negativity for next to no reason.
I have had no problem with Jay at all his customer service has been wonderful to me. I bough a trick once and it was missing a piece and I let them know and instead of just sending me the piece they sent me an entire new trick
honestly his having a high opinion of himself is just part of his act