Lets take a look at some reviews to get a sense of how this card performs. First we head to The Tech Report. The conclusion is pretty clear, the Radeon R9 290X beats NVIDIA's GeForce GTX 780 and GTX Titan while costing significantly less. The downside however is that the card draws about 40W more power than the GTX 780 during gaming, this results in load temperatures of up to 94°C and very high noise levels (50.9dBA in Uber mode). It seems AMD squeezed all it could out of this card, leaving little overclocking headroom with the stock cooler.
AnandTech writes the 290X is definitely a steal at $549 because it not only beats the GTX 780 but ties with the GTX Titan.
It looks like AMD has the performance crown for now, but the real question is how long they'll be able to keep it. NVIDIA has the GeForce GTX 780 Ti coming up soon and this card is anticipated to outperform the Titan. Additionally, NVIDIA also also expected to cut prices to make its cards more competitive with AMD's latest release.