An Epic Games community coordinator has posted the Bulletstorm PC system requirements on the Epic Games forum.

Bulletstorm requires the following minimum configuration:

Operating System Windows XP (SP3), Windows Vista (SP2), or Windows 7
Processor Intel Core 2 Duo, AMD Athlon X2, or equivalent, running at 1.6 GHz or greater
Memory (RAM) 1.5 GB
HDD Space 9 GB available
Video Card DirectX 9.0c compatible, 256 MB of VRAM; NVIDIA GeForce 7600 GS, ATI Radeon HD 2400 Pro 256 MB, or greater
Soundcard DirectX 9.0c compatible, 16-bit
Disc Drive 16X CD/DVD Drive
Network Internet (TCP/IP) connection

The following configuration is recommended to run Bulletstorm:

Operating System Windows Vista (SP2), or Windows 7
Processor QuadCore 2.0 GHz
Memory (RAM) 2 GB
HDD Space 9 GB available
Video Card DirectX 9.0c compatible, 512MB of VRAM; NVIDIA GeForce GTX260, or ATI Radeon 4870
Soundcard DirectX 9.0c compatible, 16-bit
Disc Drive 16X CD/DVD Drive
Network Broadband Internet (TCP/IP) connection

Quite reasonable minimum requirements then, and the recommended system isn’t too daunting either. Also, feast your eyes on the Bulletstorm Halo 3 advert parody.