rumoured performance details regarding AMD's Barts-based HD 6800 series have leaked online, and although these numbers are far from being confirmed, they do make sense as the upcoming HD 6800 series ends up marginally slower than the HD 5800 series and a bit faster than Nvidia's GTX 460 card.
The first results are coming from XFastest website and show the performance of both the HD 6870 and the HD 6850 in 3DMark Vantage and 3DMark06. The HD 6870 scores P16270 and 19480 which is a bit slower than the previous HD 5800 generation. When compared to the GTX 460 (256-bit 1GB), even the HD 6850 (Barts Pro) ends up faster.
This does make sense as due to the new, unconfirmed, AMD naming scheme. Basically the upcoming Barts HD 6800 series should replace the Juniper based HD 5700 series while the Cypress HD 5800 replacements, Cayman based cards, should come a month later.
These preliminary scores show that the Barts based cards feature impressive performance and certainly have a bright future. Clearly, that the upcoming Cayman-based boards and the dual-GPU Antilles card will certainly look just as good. The mentioned naming scheme might bring a certain level of confusion to the market, but in the end, it will still follow the good old, "higher number is a faster card" theme.
You can find the rest of the results here