Well, I suppose I should be the first fanboi to say...
I downloaded it in about 20 minutes at 6:30pm in the UK. Shoved it on an iPad 2, which seems to be coping fine so far. No audio problems that I can see in either Garageband or music playback.
Not an unalloyed delight; the visual design will take some getting used to, but generally a quite useful update.