Using a two thumb-stick control system in any game takes a lot of practice. I've never found FPS style games accurate enough on consoles and using one stick to control character movement, and the other to control angle of view has always been a lot harder than the keyboard and mouse combo.

I have however got to grips with dual thumb-stick controls in racing games now. One to control steering and the other to control throttle and break. To begin with I just couldn't get the hang of that system and always reverted back to buttons for the accelerator and break, but after playing MotoGP a lot I've now found I can use this system well and it is much better than buttons as you can hold the throttle open at specific amounts for cornering and in traffic for games like GTA. I still hate console FPSs though.