I just had a go at the demo. I was somewhat underwhelmed. I'd seen the E3 trailer:
http://www.youtube.com/watch?v=Ko9xC6TMdiw
... and read reviews making comments like it "delivered on the promise" of that trailer.
Maybe I expected too much, but that trailer looked really intense warzone with lots going on. The demo was a linear experience with only 3 set pieces (blow up the bridge, the APC shootout, the warehouse shootout).
I thought "1 rifle" was a bit annoying, but I didn't really try to use the pistol. I would have liked to run around with a rifle and the missile launcher as back up. 1 rifle is realistic maybe, but not as much fun.
Grenades did work well and I liked pulling out the pin then waiting for a bit ("cooking" it?).
And yeah, using cover will take practice but it looked like there were a few technical options. I found I would peek and line up the sights, drop back into cover, then just pressing fire automatically leans out and shoots at that spot.
Finally, leaving the demo running for a bit shows a scene from later on with the squad taking on a heavily armoured dude with a gas tank on his back. It inspired me some what as it showed the main character sprinting from cover to cover and moving effectively.