Across the board we've seen some good gains from the HD 4890 when compared to the HD 4870. With that said, though, it's not next generation gains, which is fine since ATI chose to keep the card a part of the HD 4800 series. If they had come out and called it a HD 5870 it would have been a lot more disappointing as we would have expected something that would really give the GTX 285 a run for its money.
Diving more in to the Sapphire part of the card, there isn't much to say about the card itself. It uses the default clocks, which are a nice increase from the HD 4870 and also the stock cooler which, while doing a better job at cooling, is also louder.
But the package is where Sapphire has really shined. While they haven't included anything in the line of full version games, they have added a nice little package which includes 3DMark Vantage, PowerDVD and Cyberlink DVD Suite. It really is a step up from what a lot of other companies offer.
If you're an ATI fan and you want to upgrade the HD 4870, this is a good jump that should give you a nice performance increase over your current card. If you're using something even older than a HD 4870 then the performance increase will be very much appreciated.
The HD 4890 is a nice card that looks to have a nice launch price. While NVIDIA are still ultimately the king when it comes to downright performance, ATI continue to offer its users and fans good valued products.