I have the demo too and yep the game is superb. I agree that submissions seem impossible to pull off with these two fighters though.
Yes, I've been trying to submit Chuck with Shogun but there's not chance in hell. I have knocked him out in a lot of ways, one of them a devastating knee to the face in the clinch.
Only lost one game to a superman punch by Chuck, not even 1 minute into the first round.