German tech site GameStar is one of the reviews websites to publish a full review of the ATI Radeon HD 4890 graphics cards. This review is in Germany, you can check it out over here. For English reviews you'll have to wait until tomorrow, within less than a day the web will be flooded with reviews of both the Radeon HD 4890 and the GeForce GTX 275.
The card was tested in several games, and also overclocked to 1000MHz with the GDDR5 memory at 1190MHz (4760MHz effective). Overclocked the 230EUR card is faster than the 300EUR GeForce GTX 285, but the reviewer says the fan got really loud.