Why isn't there an AliensRL topic yet?
Anyway, I really like many aspects of AliensRL as it is right now. Weapon balance seems about right and you must really hunt for ammo until you find a good store of weapons of different sorts. As a 7DRL it has lots of polish.
But the thing I love to death about it is the interface. It's smooth, and even though I love a "remember where you've been" function in roguelikes, having the blueprints of the building visible outside your LOS really adds to that "I'm in known territory but I don't know what the hell else is in here with me" feeling.