I have just downloaded and finished the demo. And apart from some fiddly touch control's I found the game great fun.

Unless the game falls apart later on it seems at least like a 7 out of 10 game. I get the feeling that a lot of the professional reviewers expectations for ps vita games are unrealistic.

Any way what do you guys think of the demo or even the full game?

I actually just got the Platinum trophy last night(really pretty easy though) and I found the game to be a lot of fun overall and I think you hit the nail on the head with reviewers almost expecting too much. The graphics are good, the weapons feel and operate good, the controls are surprisingly good, and the environments and enemies are pretty varied. The negatives are the story is generic, not bad just nothing special, there are limited guns, and if you like a lot of multiplayer modes then there aren't many. I am actually probably going to spend a little more time with the multiplayer in just a minute.

Also multplayer matchmaking is fixed.

Worst part about the story is that the variation dies after the second half. Plus, you can beat it in about 6 hours and get every possible trophy, making replay value zilch to none. Haven't tried out multiplayer yet, so can't judge that.

I just finished the game last night. It was enjoyable. Controls pretty well. The grenade throwing is way better than it is in Uncharted Golden Abyss. Story isn't as good as the console version, in fact, it's pretty much a throw away. Its premise is good, they just don't execute on it. Level design are nice, but linear. But if you are looking for a decent FPS for Vita, you can't go wrong with Burning Skies. And as mentioned above, it is easy to get the trophy's in like one sitting.

I played a little bit of the online and it actually works well. It can take awhile to find players, but when it does it's usually full rooms. Didn't experience any lag when I played.