AMD's Radeon HD 5770 offers a healthy performance boost of more than 25% over the last generation HD 4770. It also brings several new features to the table like EyeFinity, support for DirectX 11 and improved HDMI audio. Another area that has been worked on is power consumption which is now lower than ever.
In order to offset their product from the competition, Sapphire has increased installed their own Vapor-X cooler on the card which is designed to improve heat transfer between the GPU and the heatsink. The cooler suceeds at that and also does so without a lot of fan noise. Actually the cooler is considerably quieter than AMD's HD 5770 reference cooler, but still audible.
We saw amazing overclocking potential on our Sapphire HD 5770 Vapor-X sample which was higher than any other HD 5770 we had in our labs so far. Unfortunately Sapphire does not include any out of the box overclock with their card, which would have made it easier for less experienced users to get the max out of their card.
When looking at the price increase of about $20 over the normal reference design card, I'm a bit unsure if it is worth from a price/performance standpoint. On the other hand, twenty bucks isn't a lot of money, but it might give you a nicer overall experience. Compared to competing products, the HD 5770 is generally priced too high. The last generation HD 4870 is available for around $150 and offers very similar performance, even though it lacks the DX11 features of the HD 5770.