I just finished the game last night on my Xbox 360 and I must say that this game is designed for a gamepad. I'm a mouse/keyboard kind of person myself and I usually mock about with the gamepad in many kinds of games on the box but right from the beginning of Assassin's Creed, the controls just felt natural.
Of course, if the PC version gets the "Games for Windows" label, then you can use a gamepad on the PC version as well, though I have yet to play a game that couldn't be played with the mouse/keyboard combo (except for Gothic )
Supported OS: Windows XP / Vista (only)
Processor: Dual core processor 2.6 GHz Intel Pentium D or AMD Athlon 64 X2 3800+ (Intel Core 2 Duo 2.2 GHz or AMD Athlon 64 X2 4400+ or better recommended)
RAM: 2 GB (3 GB recommended)
Video Card: 256 MB DirectX 10.0–compliant video card or DirectX 9.0–compliant card with Shader Model 3.0 or higher (512 MB video card recommended) (see supported list)*
Sound Card: DirectX 9.0 or 10.0 compliant sound card (5.1 sound card recommended)
DirectX Version: DirectX 10.0 libraries (included on disc)
DVD-ROM: DVD-ROM dual-layer drive
Hard Drive Space: 12 GB
Peripherals Supported: Keyboard, mouse, optional controller (Xbox 360 Controller for Windows recommended)
*Supported Video Cards at Time of Release:
ATI RADEON X1300-1950 / HD 2000 / 3000 series
NVIDIA GeForce 6600-6800 / 7 / 8 / 9 series
Laptop versions of these cards may work but are NOT supported. These chipsets are the only ones that will run this game.
NOTICE: This game contains technology intended to prevent copying that may conflict with some disc and virtual drives.
I merely meant that the role the mouse plays in the Gothic control scheme is virtually negligible to the point where one is almost better off only using the keyboard.