If your computer can play the latest modern 3D games, then it should have no problem running Guts and Glory. If you're using an older computer, try lowering screen resolution and quality settings. It is still in early development and I have done very little optimizations, so performance should improve with time. If your graphics card is quite old, then the game may not work for you in its current state.
The easiest way to find out is to try the free build at IndieDB.com!