It's not the same. It runs much much hotter and a whole lot noisier.
It produces 60db at peak load. That's like sitting in a busy restaurant with background music except instead of having a fun and interesting conversation it's a whine of fans spinning. Imagine having that noise in your own home all the time.
I would wait if I was in the market for a card that expensive. There will be a heap of people selling 290x's if the 390 performs well.