Multi-mon is supported out of the box with Hor+ gameplay.
Additional interface fixes (centered HUD, non-stretched subs) should be automatic for Eyefinity users, and can be easily enabled through the registry:
1) Windows Start menu / Execute... / regedit
2) On the left panel, navigate to: HKEY_CURRENT_USERSoftwareUbisoftPrince of Persia - The Forgottent Sands1.0Engine
3) On the right panel, double-click EyeFinity and change value to 1.
4) Thank fluxetreflux for the tip !
4:3
48:10, EyeFinity 0
48:10, EyeFinity 1