One thingy we didn't mention yet are the playable Alpha system requirements:

Minimum
Operating system: Windows XP SP3 / Vista / 7
Processor: Core 2 Duo Processor or Equivalent
Memory: 2 GB RAM
Hard disk space: 2 GB free hard drive space
Video: 256 MB DX9 Compliant
Sound: DX 9 Compatible Audio
DirectX®: 9.0c

Recommended
Operating system: Windows XP SP3 / Vista / 7
Processor: Core i5/i7 or equivalent
Memory: 2 GB RAM
Hard disk space: 2 GB free hard drive space
Video: 512 MB DX9 Compliant with PS 3.0 support
Sound: DX 9 Compatible Audio
DirectX®: 9.0c

These could very slightly change while we get closer to Gold.