I liked the demo (and a preview-version I got to play briefly), but I would have preferred a remake of the original instead. Settlers II is bigger, yes, but it isn't really better than the original. It feels slower, and not all the "new" elements are implemented as well as the core game. Besides, it lacks the all-important "random" map generator of the original. I want to settle new and unpredictable lands, not carefully designed and balanced levels.
One thing I definitely don't like with the new version (I can't actually remember if it the original Settlers 2 was like this as well) is how you can't make roads through forests. That, to me, seems like an artificial limitation that serves no other purpose than to complicate an aspect of the game that really doesn't need to be complicated.
Still, it's good that the classic Settlers-gameplay is making a comeback. I am definitely looking forward to playing it. Too bad they're not including split-screen two player. One would think that with todays USB-mice and all, it would be just as easy to set up a two-player game as it was on the old Amiga, but I suppose most developers don't even consider this option these days.