[fpgeek]

You've been able to share apks "forever" (since before the G1, I believe), but Google's official beta-testing framework (Play Store integration [don't even need unknown sources], rolling/controlled updates, beta test volunteers, etc. plus the pattern of tying that to a G+ community) is brand-new since I/O this year.

And it seems to be a compelling package - pretty much every app beta I care about has switched to it (even those that already had an existing off-Play-Store setup).