[jjcm]

Out of curiosity, why is there a flag to enable it? Why not have it on by default? From what I understand, there's no downside to hardware acceleration - the offload to the GPU uses less power, it's rendered faster, and it is a better user experience. What's the edge case that requires this flag to be off?

[zmmmmm]

From TFA:

    some operations behave differently when hardware acceleration enabled

So they've been conservative. I kind of wish they hadn't - 3.0 is a big enough version jump that people understand there's going to be a few glitches, and there are almost certainly a large number of apps that don't use any of the small number of listed APIs that change their behavior under hardware acceleration. Those apps that do use the APIs could be autodetected I would have thought and have hardware acceleration disabled automatically.