Well, played AC a bit this afternoon...
1920x1080, High Settings
Intel Core 2 Quad Q9550 (4 x 2,83 Ghz)
8 GB Ram
Gainward GTX 570 Phantom (comes with a massive 3rd-Party cooler and slightly OCed)
Gigabyte EP45-DS4 Mainboard
Win 7 Ultimate x64
Getting about 25 to 30 fps...
I´m VERY pleased about my 5 years old rig (Graphics card updated about 3 years ago).