Yeah and no.
For 2 and a half year I had a HD 3870 and I know, fglrx sucks until today.
I changed it really fast to a 275 GTX and I know, nvidia is a better driver and has better performance then the opensource radeon driver, but opensource > closed source ;)
Unfortunately there is no overclocking support in nvidia for >4xx GTX.
(Excluding BIOS mod)
But there is a lot going on with radeon:
UVD is working with kernel 3.10:
http://www.heise.de/open/artikel/Kernel-Log-Was-3-10-bringt-4-Treiber-1897241.html
a new direct rendering manager, dynamic power management support with kernel 3.11:
http://www.phoronix.com/scan.php?page=news_item&px=MTQwNjA
http://lists.freedesktop.org/archives/dri-devel/2013-July/041313.html
A year ago radeon was quite competitive with fglrx in Xonotic:
http://www.phoronix.com/scan.php?page=article&item=amd_r600g_compete12&num=12
Linux 3.5 boosted the performance of radeon:
http://www.phoronix.com/scan.php?page=article&item=amd_radeon_linux35&num=1
At this benchmark, the 6xxx has nearly the same performance at Xonotic with fglrx as with radeon
http://www.phoronix.com/scan.php?page=article&item=amd_radeonsi_catalyst&num=3
Here is a speed up with another LLVM Compiler Backend on HD 4650:
http://www.phoronix.com/scan.php?page=news_item&px=MTQxMDM
There are some patches improving the performance in some situation not merged yet
It is logical, that the newest radeon cards perform bad with radeon, but I don't want the newest ;)
See here the list:
http://xorg.freedesktop.org/wiki/RadeonProgram/
The most programms were tested with Mesa 7.xx, Mesa 9.2 is the current version
http://www.phoronix.com/scan.php?page=article&item=amd_mesa711_mesa92&num=1
Don't get me wrong, but i wanted information from somebody really using it with wine. (if these people exist ;))
Phoronix don't have much wine benches :(
Edit: This video is 2 years old:
Crysis 2 on RV770 Chip (4850 or 4870)
http://www.youtube.com/watch?v=XZ_T_xepfW8
Edited by Smon