Nice to have some assistance again, even if it is -them-. They make some interesting sounds and as we hear from a terminal, they're not exactly on our side - I find it annoying that we have no way of telling the guys on our side about this and this is the first scenario where I've felt this ... the no free will concept really kicks in. We had no choice in aiding cain then we get told off about it. We find out these guys are nasty but we can't tell the others ... a little annoying.
I found the level layout not so conducive to the gameplay style required with a lot of backtracking - it's a bit confusing and map view comes in very handy. I think this level introduced the new tougher alien type, with M1 juggernaut style machine guns. Probably nasty, but I'm playing on Kindergarten ;).