In perhaps a nod to the VMware that Chris prefers, another version update I think best skipped -- this makes 3 or 4 in recent memory. :(
This was an ambitious update so I expected a few problems, but it's also the 1st time VBox has caused Bluescreens -- 3 of them -- & it wasn't even running [probably driver issues].
Other, more minor issues have been reported, plus some frustration &/or angst at the way they've added USB 3 support, or rather the way they've sort of advertised it. It implements a USB 3 layer rather than actually emulating a USB 3 chipset, so no drivers for a win7 guest are supplied. Later versions of Windows guests are supposed to be OK, but didn't get that far to test.
Definitely back up before adding this version [if anyone decides to try it] -- being able to restore a backup saved me -- as I've also read reports of problems after trying to roll back to the prior version of VBox.