I'm pretty sure they have done major internal changes, mostly to data handling. The performance of the menu is much better. There was an extra step during installation where the system partition was optimized. Patch download procedure seems to work a bit different for large ones. Lots of hints like that, including new bugs like missing DLC downloads (which will hopefully be fixed with Beta 4 or at least the stable version).There's nothing major to test.
Sony might see that a bit different. Beta testing is very much automated these days, the importance on manual tester feedback is lower, because a lot of useful data is automatically collected.Pointless.
Of course you can wish for cool new features, but IMHO reliable performance is desirable too, so I don't feel let down. Also a handful of the minor features are nice to have, too.