It is important to note that the demo is the first level in the game and holds your hand a lot in what to do. The mission isn't as open ended as the rest of the game because it is a tutorial level. Its a good thing for new gamers to the series but annoying for us veterans.
The graphics are outstanding. I ran everything maxed with both AA and AF at 2x and the resolution at 1024x768. Ran perfectly. My system is an Athlon 3200, 1GB Ram and a Geforce 6800GT 256MB. I love the soft shadows and the very detailed environments. The character models look a bit plastic-y in bright light, but better indoors.
There are a lot of moves that 47 can pull off now. You can throw people off balconys, hide bodies in freezers and boxes, take enemies as human shields, disarm opponents, knock them down, etc. The tutorial really showed off everything you can do and all the tools you can use in the game. A headshot is a headshot in this game so its good to see them go down in one shot. Stealth is easy to master and gunplay is as well. There are a lot of weapons to be used.
The demo level isn't very open so there is only one true route through it, but given this is a Hitman game the rest of the levels are for sure open just like the rest of the games. I just hope the full game does not turn into a trial and error approach.
Overall if you liked the demo, give the full game a try. The sound was excellent with the soundtrack being great as usual and the controls are much better now, not sluggish at all like before. A+ demo, and the PC version only will cost $39.99. Its a steal.