I'm kind of surprised by some of the attitudes expressed on this thread. Too many points to make, so I'll try to summarize.
Sometimes building a program on a platform isn't about whether it's worthwhile or not, sometimes it's just about discovering whether it can be done. Sometimes it's even just about personal accomplishment.
Yes, it's based on 0.37 like all the other MAMEforAll builds. MAMEforAll is a fork of MAME, maintained for it's portability. Just because it's "old" doesn't mean it's "bad". Lots of emulators get ported in this fashion (e.g. FCEU, SNES9x, etc.)
Yes, mobile gaming still leaves a lot to be desired. But that's why I bought the Xperia Play. I fricken love this thing, and now that MAME is available for it, that's the final nail in the coffin for my GP2X. Even without the gamepad controls, the 80s games that this MAME faithfully emulates are not so complicated that an on-screen control pad can't suffice.
Convergence is the name of the game. PCs, phone, tablets... they're all converging into one ubiquitous device. Sure, phones are bit on the slow side compared to PCs today, but don't bet on that being true in less than a decade.
It just seems like a lot of people are expressing the thought that if they don't think it's worthwhile, it should never be attempted. And to me, that sort of flies in the face of MAME's philosophy.