I've played half the demo version, and am impressed. More later.
(Got to the bit where I was finding the sewer grate. Realised I couldn't find it and also realised it was six-o'clock so had to go to the pub)
Think you're being a little hard on the non-linearity. There's only one path through the level, but there's multiple ways to deal with the problems (i.e. The soldiers Patrol), allowing both stealth and combat. Deus always had a nonlinear episode with a fairly linear plot.
Will be dropping Gand a line. Since my main feedback is a story-line based subquest I think could and should be phrased better, it's a good sign. The fact it's relatively well written is another big plus.
(My plot hole is the quest given by your quasi-girlfriend: Go ask the doctor about how her friend is in the hospital. I believe there's several phones in the room - why not use them to do it herself. To make it make sense in the game would be something like "You've always got on well with the Doctor - can you see if you can get a little more out of him than I can?".)