Wow, there sure are a lot of people here who really don't seem to know what they are talking about.
The assumption that people seem to be making is that because the 4870x2 is DirectX10.1 hardware, that means it won't be able to run DirectX11 games and benchmarks. That is simply incorrect and not the case at all.
The 4870x2 should have little if any issues running any DirectX11 game. This applies to all DirectX10 and 10.1 hardware.
DirectX11 is a strict superset of DirectX10.1, which itself is a superset of DirectX10. Compatibility is as simple as shedding the small subset of feature that are not present in DirectX10/10.1.
When a DirectX11 program is run, it will first make a quick query to determine your card's "feature level". There are separate feature levels for DirectX11, DirectX10.1, and DirectX10 hardware. Once it has made that determination, the game will continue to run, in DirectX11, making use of all the features in the highest available feature level.
There is even a separate feature level just for 10.1 hardware, instead of grouping it in with other DirectX10 hardware. That means DX11 games using the DX10.1 feature level will still be taking advantage of the advances DirectX10.1 made over 10 that were not taken advantage of in the past due to Nvidia's lack of 10.1 adoption, advances which ultimately became a part of DirectX11. It's also important to understand that a game running in DirectX11 using the 10.1 feature level is NOT the same as the game simply running in DirectX10.1, as there are numerous improvements in the DirectX11 API itself that are not dependent on the underlying hardware.
http://msdn.microsoft.com/en-us/library/windows/desktop/ff476872(v=vs.85).aspx
So while your card will not have all the benefits of a card using the DirectX11 feature level, running a DirectX11 game on 10.1 hardware is really not a bad place to be. The main noticeable feature you are going to miss out on is Tessellation, and when I say "noticeable", keep in mind that everything is relative...
Tesselation enabled (DirectX11)
http://gotnorice.no-ip.org/tesson.png
Tesselation disabled (DirectX10.1)
http://gotnorice.no-ip.org/tessoff.png
So there are differences, but it certainly doesn't involve not being able to play DirectX11 games. I'm a proud current user of 2x 4870x2 in Quad Crossfire and it has held up with age so well that my Quad-GPU config is even competitive with a 7970 in certain situations. Almost all of the games I play are DirectX11, and they all run perfectly.