Yeah I've completed it. Now when I play it i'm usually trying to complete it without casualties. Apart from Burke. He deserves to die.
The trick to the second one is to have the flamethrowers alive to lay fire on the ground and stop the aliens from getting too close when you're fleeing through the air ducts. Which means in mission 1 you really REALLY want Frost to survive, even though he only has a pistol. He has a flamer in the second mission, as does Drake. So you need to make sure they make it out of mission 1 alive.
For the final mission it's helpful if you can make sure Apone, Hudson, Ripley, Drake and Vasquez get through. The rest are useful but not critical. Though the more flamers you can take with you the better.
