I had such an awesome experience in this game I feel the need to share it.
It was like this:
I had just downed a UFO and was investigating the crash site. After popping a few Insectoids outside of the actual ship, I start making my approach. I'm playing with Iron Man enabled (only on normal, though, as I've never played any of the other games), and beacuse of that I am very careful when advancing. Anyway, I set up a sniper on a hill outside of the UFO and moved slowly inside of it. In the first room, there was nothing. I had cover in the center and around two doorways, left and right. I start setting up my squad to move through the doorway on the right, when suddenly, two Floaters burst through. An assault trooper on Overwatch takes a shot at them, but it goes wide. One of them moves outside through one of those large force fields and the other one moves towards a support at the rank of squaddie. However, in doing so, it moves into the line of sight of my sniper who's stationed outside (with Squad Sight, otherwise it would have been way too far off), and takes a bullet to the face. The other Floater goes down without a fight.
Moving into the central room of the UFO, I am a bit reckless and have only one unit on Overwatch. One of those aliens that materializes out of thin air suddenly... well, materializes out of thin air. The guy on Overwatch takes a shot at it with his laser rifle, misses, and destroys the wall behind the alien. My sniper, who's still sitting on the hill outside, can then land a reaction shot through the newly made opening in the craft, effectively ending the mission.
It was awesome. I love this game.