I've managed to have some bloody good fun playing AVP2 MP demo but it seems to be almost in spite of the game dynamic the Developers have created rather than being facilitated by it.
I have a feeling that a lot of what people don't like about the gameplay comes down to a Q3 Deathmatch fixated decision to play balance the three races so that they're individually similiar in terms of power. I say similar, because in the demo level at least, ommisions mean that this balancing act is far from succesfull. The Alien is especially slighted in this respect.
The Alien is JUST TOO FUCKING SLOW, and the reason for that is so that the Marines and Predator can get a chance to employ their ranged weapons. The net result, however, is that unless he uses Ambush tactics rather than rushing tactics the Alien is dogmeat. How well does camping work with Hand to Hand weapons? Exactly. Life as an Alien usually revolves around constantly hoping that green blur on the far side of the level doesn't see you.
The marine can be a good choice in Death Match, but generally only because the Predators are shitting themselves about Aliens (making Marines invisible to them) and the Aliens are usually steaming over that blue homing cannon the Predators have and are gunning for them. Being beneath notice gets the Marine a lot of frags. Also, Marines are a totally different prospect after armouring up to 200% and equipping with Grenades.
Yes, I know about the vision modes, but the Predators Shoulder Cannon gun is TOO GAY FOR WORDS. I mean, I could have accepted limited homing, but whilst playing the demo as an Alien Drone I dropped down that chimney like pit in the Central Processor, and the fucking thing followed me down there like the Proton Torpedoes in the Death Star run.
The balancing of the Predator relies entirely on there being multiple other species in the game. Otherwise he sits on the respective vision mode on top of a nice camping site and is unbeatable. A player at my office who plays Predators recently tried to downplay this by pointing out that after 6 or so shots of the shoulder cannon he usually has to recharge-heal-recharge, and that he generally gets fragged during this time. That puts the Predators at three kills per Spawn, and everyone else on an aggregate of three Spawns per Kill.
The Marines can have good sucesses, but you just try playing a more "canon" game where its a small squad of Marines versus a single Alien or Predator. It gets dull quickly, unless the Predator uses his Shoulder Cannon in which case it means that life is only marginally harder for the Predator - so long as he only tries for one kill per Ambush, things aren't any more difficult for him.
Bottom line, the designers seem to have made a number of play balancing decisions based around making Deathmatch fairer. Personally, Deathmatch is the LEAST important part of the game for me, after Co-op and Single Player, and I fear very much that those other two game styles have suffered at the hands of "Quakecentric" game design.