I hate to sound distrustful, but I suspect they release new versions and then rely on public testing to straighten things out. The fact that boolean mesh export simply doesn't work any longer (that's not a "detail" one should miss before releasing something!) seems to somehow substantiate my suspicions.

I installed 6.3, but kept 6.1 installed. I'd advice to do the same, but I don't know if there is any drawback in doing so.

EDIT: I don't think they added anything significant (or anything at all?) to "content" (but I may have missed it) and I didn't do any "render speed test".