What I do now for most tunes is create an interesting chord progression/arrangement, then save as WAV to re-import into iTunes for live performance. But for more complex or interesting tunes, I may save it at the same tempo in several styles or variations. Then I go into Adobe Audition or Digital Performer and mix and match the tracks to get the arrangement i want - change style, copy/paste tag endings or intros, etc.
Not as simple as pressing Play, but it lets me avoid boredom from too much same old swing or pop grooves. And only takes a couple minutes, no big deal.
I still desperately need a good jazz shuffle, though. The rock shuffle is good for rock, but unusable for jazz grooves. And the swing isn't beefy enough for real down-home blues. (But they are both great for what they do - I'm not complaining, just wishing/hinting for the next Style Pack.. This is a ridiculously amazing app...)
BTW, the Latin/Swing is awesome - and works perfectly with the Latin for external editing.