The Sony A77 is a dog in low light at high ISO, I'll just say it like it is. But it had no problems shooting in low light.
Yes the A99 is a game changer. No longer having to deal with stigma of bad performance at high ISO in low light, now the A99 can box against the other top end bodies and show its advantages over CaNikon.
Looking at RAW files for both, I can see the Nikon has the edge with no fixed mirror like the Sony, but it's so very slight, you'd have a hard time seeing it. Both use similar Sony image sensors, with the key difference is that Sony gets phase detect sensors on the image sensor itself, I don't think Nikon does.
Bottom line, compare the new Canon 6D and the Nikon D600 you will see that the A99 is a more full featured full frame body, and the price reflects it. For still photos only, I'd be more than happy to take the Nikon, but you give some things up.
The Sony shoots faster at full res, the only one to offer 60fps at full 1080p, for slow motion work, it has dual card slots, fast phase auto focus available for video, and the BIG one, focus peaking that CaNikon does not have. I also like the swivel screen, and the EVF to see things and graphics in real time. You pay for all this though, so for the money the A99 isn't always the best, but yes it is a game changer camera.
For 3K US dollars, yes a black magic cinema camera is the best, but you lose a lot, and to get the most out of it, you need to shoot 2.5K RAW. More time consuming, and you need serious storage and a serious PC or Mac to handle it. The BM camera smokes up 256GB solid state drives with just 30 minutes of footage. For quick footage, and less demanding things like something that will only ever be seen on HDTVs and not movie theaters, dSLRs I think are better.