Good review
A few more words about the wall walking: The gravity walks are a really nice feature, but is taken a bit far in some parts of the levels. Yeah it's a game, but there are places where including them is excessive. It is obvious that they are a new toy the designers were playing with. It's sort of the same phenomenon television went through when color tv was invented... where all of the new shows were done in obnoxiously blinding saturated colors.
That said, I really do like them. For people who get queasy playing FPS's, keep a trash can nearby. The movement of walking forward or sideways 90 degrees over the top of a wall to be standing upright on it can be a bit disorienting to say the least.
For a single player game, where you are likeley to have the experience once or twice per level, the disorientation can be a little annoying. I played the demo twice, and the second go-around made me realize that I had not understood my surroundings very well the first time. This might make the single player game interesting to play more than once. In the deathmatch maps, where you can learn the levels, the disorientation can be a blast. The two included deathmatch maps have extensive use of gravity walks, gravity re-orientations, and portals, such that it takes a fairly good amount of time to figure out the maps and get used to them. You have to think a bit differently to understand the maps well.
There is a lot more necessity to look up and learn where all the gravity walks enter and exit rooms. It is also important to learn the direction of gravity relative to the direction you are currently walking. This can help you realize places to get to that may at first seem inaccessible. For example, if there is a large pipe running through a room, and a gravity walk goes up the wall and across the ceiling, you can walk up it, position yourself over the pipe, then jump off the walk. Your perspective flips 180 degrees as you rotate to be standing on the pipe. I have not had a problem with queasiness since the sprite-based shooters, but this game brings a tad of that back if you do too much flipping around. Still, I am having a blast.
I just wish the demo had a couple more deathmatch maps.