Nice idea with the 'lines of sight' of the guards. It's fun to sneak past the guards as the controls are very smooth. I did accidentally 'shoot' my sword a few times though which I put down to my left handedness.
I didn't using the hiding much - you could improve the level design to make it more necessary. Also I wonder would it work better with a smaller scale so that you could see more of the map and hence the enemies - they tended to be off screen a lot.