I just received my evga 7900gt in the mail yesterday and without a volt mod yet, I'm seeing a huge performance increase.
I did own a x800xl 512mb card and here were my 3dMark scores:
03 = 10152
05 = 4100
06 = 850
New 7900gt @ 562/882
03 = 19630 (+96%)
05 = 7750 (+94%)
06 = 4740 (+278%)
I'm very impressed, I'll give an update after I volt mod. Also, I would like to point out how easy overclocking is. I installed the drivers after removing the ATI ones and easily installed Coolbits, then used the find optimal overclock setting button and this is what I got.
I know I can push it more, we'll see how much more real shortly this week
Also, does anyone know some good software for nvidia cards to check for artifacts and maybe some software that will always display current temps and fps in game like ATI tray tools did, thnx. 
Specs:
Intel 530J 3.0 Ghz @ 3.4 Ghz
1GB Corsair DDR2
450W OCZ Mod Stream / 26A 12V
Audigy 2 ZS
Gigabyte 945P-G Motherboard
I did own a x800xl 512mb card and here were my 3dMark scores:
03 = 10152
05 = 4100
06 = 850
New 7900gt @ 562/882
03 = 19630 (+96%)
05 = 7750 (+94%)
06 = 4740 (+278%)
I'm very impressed, I'll give an update after I volt mod. Also, I would like to point out how easy overclocking is. I installed the drivers after removing the ATI ones and easily installed Coolbits, then used the find optimal overclock setting button and this is what I got.
I know I can push it more, we'll see how much more real shortly this week
Specs:
Intel 530J 3.0 Ghz @ 3.4 Ghz
1GB Corsair DDR2
450W OCZ Mod Stream / 26A 12V
Audigy 2 ZS
Gigabyte 945P-G Motherboard