There have been quite a few posts on this game on the W&W forum. I agree -- I wish the demo did more, so that you could get a really good feel for it. You can reprogram the keyboard (not sure about the mouse button, but I suspect so)... go into Options (or is it Settings?) from the main menu.
I think the demo is also a bit hyperactive when it comes to random monster encounters. There are far more than I've seen in the most prolific of games that I can recall.
A patched demo, or even a second demo, would be welcome. A game where they've fixed all these minor annoyances would be even better
Apparently, it is now scheduled to be available towards the end of the month. Time will tell...