Never played LP1 but I had always heard good things about it from hardcore gamers, and any game with a grappling hook deserves a second look in my opinion.
Let me just say that after running the demo only twice, LP2 was easily my most anticipated game of 2009-10, surpassing AVP & even Crackdown 2, which I did not think would be possible! I think this could be the case for a lot of other players as well, as I have heard nothing but glowing praise from most of the microphone equipped users on XBL.
I've been a long time FPS addict since Wolfenstein, and Doom & Quake were the battlegrounds where I cut my multiplayer teeth. These days I've been looking for new and inventive takes on multiplayer versus and cooperative shooters, and to say they are in short supply is an understatement. Halo & Gears are so painfully derivative and frankly self absorbed to the point of being scared to take chances and think outside of the box, less they dare to dissapoint a fragment of their player base with something novel or unexpected.
LP2 is nothing short of a breath of fresh air for me, which is an incredibly surprising thing to find myself saying after being not only an FPS focused gamer for over a decade, but an incredibly jaded one at that. I am not much one for pro and con lists when discussing works of art, so I will attempt to avoid such a binary disposition from here on out.
I enjoy the fluidity of the movement mechanics an immense deal. Never before have I felt "free" when playing Halo or Gears, always have I felt like a rat in a maze vying over the cheese, and the cheese is always a Rocket Launcher or Armor or Camoflauge item in the same damn spot. The rolling, even with the i-frames, is a welcome addition to the sprint feature, and in combination with the anchor really makes for some interesting sequences of events. Quite often I will find myself rolling "towards" my camera while running away from the Salamander tongue lashes, keeping all of this cinematic glory focused on my HDTV set while sacrificing nothing in the way of precision controls and navigational abilities.
I could spend a paragraph discussing just the anchor itself and the button presses that modify its behavior, suffice it to say I am incredibly satisfied with it - from the ability to change the wall mounted hang to the vertical zipline, to the quick detaches and forward jumps, it all executes so consistently! I've only seen a few instances of it glitching out, and in those cases the Anchor would fail to attach to a section of geometry and it would stay projected in space, locked in a strange proportional way to the distance it attempted to travel before failing. In a few seconds and/or steps it would retract back into my pack and be usable again, without any ill effect. Of course it is natural to desire the ability to hook while jumping or falling, but without logical cooldowns or other arbitrary timers this would get ridiculous - I know for a fact that I would abuse it, and the game wouldn't be better just because I could do that.
The Vital Suits... wow, where to begin? I believe I grabbed the VS Shotgun before the first unit by the initial Battle Gauge, and my first thought was "I wonder if I can put this on the VS?" Like a kid who wonders if he can put a square block in the square hole, you are just thrilled when things "make sense" and the world around you functions as expected, it is very rewarding. Within a few short matches I had begun to grab the mech, jump it up to the shotgun, attach it and return to lay waste to the Salamander. What a wonderful demo, to allow such exploration and foster improved decision making without jamming tutorials down your throat or requiring you to read a bunch of abstract concepts to wrap your mind around the game design. By the end of the night I believe my 3 friends and I had played through the demo a dozen times, and by those late hours of the night, not a single one of us had gotten tired of doing anything and everything in our power to rack up as many points as possible and lay waste to that Salamander! I believe one of my friends alluded to the fact that he would play through the whole game with that fully kitted out 3 man mech if he could, that gave me a chuckle 
I'm interested to see how the different weapon loadouts and preferences will work in multiplayer, but again this is one of those areas where I am entirely trusting in Capcom to do something not only differently, but to do it well. Compared to most folks in this thread, my friends and I all seem to love the (?) Boxes that pop out of his legs and of course during his death spiral, it takes us back to the MarioKart days and immediately I could see that the database relationships were nonexistent and these boxes were probably indicative of collectible items or armor permutations, which I assume and hope to be the case in the final game. The only issue with me is that having not played LP1, I thought those were the T-Eng drops before I realized those were the little orange puddles that drip out of his wounds. As another poster mentioned, I would have liked to see more definition and special effect indicating the importance of the T-Eng drops. Compared to the bright yellow boxes and gauge at the top left of your screen, the muted orange and pale yellow T-eng blobs fade into the grass and are hard to see unless you run over them relatively quickly after being dispersed. I don't have problems locating or picking them up, but I think it would be beneficial to increase their visual impact to let players know how important they are, relative to the goofy boxes anyways 
It also seemed as if there were three "speeds" of the intestinal waterways, 75% of the time I could run back towards the esophogous on the first "flush" and go for a 20AK kill streak before getting permanently dumped. It seems that after x amount of damage to the core, the speed will always ratchet to the highest setting on any secondary infilitration attempts. Honestly this kind of behavior is something that is indicative of me overplaying the demo, because when you think about it this is not something that will be so rotely repetitive in the full game - remember this is just one boss, and for the most part the AI behavior and interactions with it are not only amazing but the best I have ever seen in any game! Small perceived inconsistencies or my inability to understand the relationships between various types of damage do not indicate a problem with the design, just my own experience and perspective, and I realize that.
One final note on multiplayer permutations - PLEASE - make them all unlockable through achievements and normal behavior. I was one of the few hundred recipients of Recon in Halo 3 shortly after the game was released, and it made my XBL experience a living hell for the next 18 months - only now that ODST is a couple weeks away have the random friend requests and spam messages begun to die down. Making an item that is on the disc that nobody can access but a select few is not only unfair, it is also bad marketing; in the sense that it creates a lot of demand for a portion of your product, but at the expense of a lot of goodwill from your customer base. Those (?) boxes were a very reassuring site and I look forward to collecting all of them!
Tangentially, I did use the flying mech to pull the stunt of hovering over the External Core while the Salamander was dying, after reading an earlier post by "velocity7" fearing such behavior. You have to kill your boost jets at just the right time to clear his clipping model and position yourself at the correct distance above the box spawn point, but I have pulled it off two or three times out of a dozen attempts. Not much else to say about it except that it is hilarious and works really well if you hadn't picked up any boxes during the rest of the round, and the rest of the people in the game will laugh a lot - they get their own boxes, as presumed
All in all this demo was so great that it led me to not only play through it hundreds of times (literally) but register an account here and share these thoughts. This game is day 1 for me and at least three of my good friends, and I really believe it deserves to sell multiple millions of copies. Honestly in a just world this game would put out enough units to equal the combined sales of ODST & MW2 - but there'd also be no war & world hunger in a just world, so it looks like we've all got our work cut out for us! 
