I just finished the demo and it hooked me all the way.
The problem is, now I cannot get enough sleep!
Last night I thought I'd play a bit (started playing at around 11:30 pm) and ended up going to bed 1:30 am :(
And it was such a bothersome ending too, since I challenged a level 6 character in the tournament and I was level 4. The battle went on very long and finally there was only the enemies last Ancient Bear and I had only my last Swordsman left. Unfortunately I lost it, even though I was so close...
naturally I have to try it again some night.

So you're basically scared by how awesome this game is :P
This is an indication of how good the game actually is lol...
Get it now!

What you described is definitely a danger with this game. For me this game (and it's sequel) were responsible for quite a few instances of "Just a little bit longer... it's 3 am already?!"

Yes, got the game a week ago, and been averaging 5.5 hours of sleep a night since...
Edit: I hate this game. 80 hours of playing in 10 days. And I already have a real fulltime job! This must be how WoW addicts feel.