Amusingly, that's actually the only use case for multi-touch that I have personally. This feature is especially useful/necessary for console emulators where pressing a button + a direction makes a sprite dash/run instead of walk slowly. Other games also make use of two buttons for some functionality.

Sure it can be done on the keyboard (which is what I do currently on the N810), but holding the device and playing that way is quite cumbersome (IMHO). I'm imagining that the face multi-touch stuff (liqbase's specifically) might actually be sufficient though. I wish I had enough knowledge and skill to try it out