There are a ton of little errors - ones that make ListInfo/SortInfo display incorrect information... I actually went through one driver and fixed a whole slew of games that had incorrect #'s of buttons listed, but the change wasn't accepted by MameDev... I sort of understand why, I think, because I changed a ton of lines of code, and made the driver a lot larger. Basically the problem was that generic macros were defined and used for all of the games, even when they weren't correct.
I would love to see --listinfo get to the point that it correctly identifies all the information about the controls for a game.
I like making input fixes - it's the one area of the Mame code that I sort of understand, so I'd be happy to work on some of the bugs you've found.