Phoronix revisited the performance the HD 7950 on the new Catalyst driver for Linux as it is no longer labelled as unsupported hardware.  That means that not only are the default clocks correct, you can use aticonfig/amdconfig to overclock the cards if you so desire.  The scaling of the card now matches the clock speed nicely and shows an improvement from the HD 6950 in the benchmarks.  You might not be able to find a Linux game which will take advantage of the full feature set and power of the HD 7950 but the card is capable of far more than providing you with pixels to slaughter.

"Here are some updated benchmarks of the AMD Radeon HD 7950 "Southern Islands" graphics card under Linux with the proprietary Catalyst driver."

Here are some more Graphics Card articles from around the web:

Graphics Cards