Ahofle: Probably milliseconds. I'm not that great of a player, but when I play a game on MAME and notice a difference, it's disappointing. I noticed these problems when not looking for them, which tells me that the problem is pretty gross. Later confirmed them side-by-side with the original, just to make sure I wasn't imagining things.
I haven't noticed a lag with buttons, but that doesn't mean it's not there. Just means I haven't noticed it.
Frizzlefried: I tried USB, PS/2, and Serial... same problem. But, since you have only used .106 and later, maybe it *IS* something fixed in a later version. Latest I've used was a very early 0.1 version.
Crowquill: When I redid my MsPac I picked up enough "remnant" laminate to do the whole game, for not much money from a cabinet shop. It is also a nicer looking pattern, though I would have gone with something that looked more original if they'd had a remnant of it. Anyway, I had to do some bondo work too, that's why I laminated it. I'm just suggesting that you check some local shops for cheap remanants if you're open to the option of repair and relamination - it might not cost much at all.
TTYL,
Wade