On first run, like the previous comment, it tries to validate your ROM files and seems like it goes through its entire internal list even if you don't have all of them. I killed it after 40 min. and it was only up to "C".

I ended up scrolling to the games I wanted to play, selecting their names, and validating just those, just so I could play it. But, c'mon, 5 hours isn't really useable.

Once in the games, I noticed a few more graphic artifacts than on MacMAME (esp. in vector games) but seemed to play well otherwise.

Coming out of games, a lot of 'unexpected quits'.

Definitely looking promising, but I'll stick with MacMAME for now.