Also on Delta, the enemies do not glow red when they are pissed off.
You don't have your default crosshairs, but it doesn't really mater once you get the laser attachment for your pistol/rifle. I never was detected with that on. The melee aliens will also kill you in 1 hit if you do not have Armor on and the ice shards hurt pretty bad if you stick around in it.
My advice on playing Delta: Save Often