So here are a few things I found that were unexpected, not sure if they are bugs or 'features':

1. Arc Throwers don't work on civilians (unlike in Original XCOM where you can stun them for their own protection).
   
2. Arc Throwers don't work on good guys even if they are Mind Controlled. Again that was a handy thing in Original XCOM to render enemy-controlled agents harmless, without killing them. Also for Panicked agents. I suspect XCOM 2012 will not let me stun a Panicked agent either. Basically you just can never select a human target with the Arc Thrower.
   
3. You can't attempt to Mind Control an enemy unit that is Mind Controlling one of your units. That doesn't make a lot of sense. So I was about to Mind Control that Ethereal, easily, but I can't do that because he's mind controlling someone else? I don't like that, poor implementation. They just should have said that the targets' Mind Control breaks, if yours succeed. Not made it an Invulnerable to Mind Control power.
   
4. You can capture alien items by having the alien mind controlled, then killed by the aliens. The items don't explode in this case.
   
5. However (and again unlike Original XCOM) you can't shoot an alien while it's mind controlled. This makes it hard to dispose of the aliens. You can use indirect fire while they are mind controlled. You can make them drop a grenade on themselves. Or just stand them in the open and set up lots of reaction fire. But it's very dumb that your own guys can't shoot at them just because they are Mind Controlled. Heck I think it would be a big problem the other way round. XCOM agents are trained to shoot aliens on sight so the Psi guy would be saying "hey, stop, stop shooting my alien!". It's not like they put a different coloured team jersey on when they come under Mind Control.
   

And wtf is up with save game file management? I can easily spend 15 min trying to find the right save game file, and very easily load the wrong one. No way to name the save file with a helpful description. No way to sort or filter on basic things like Game # or date/time. Files have to be deleted individually and you have to then scroll back through the entire list again each time, it doesn't hold your position in the list. And doesn't allow multiple select for deletion. And if you delete files piecemeal, it becomes even more random to find the right file.

 

And if you archive off game save files into a subfolder, the game kindly and silently deletes them all at next startup.

 

This is really, really poor implementation. And a PITA.

I would say it's a bug that the Mind Shield is described in-game as defensive only. Pretty sure it isn't, if equipped by a Psi Operative it increases their Will for offensive purposes as well as defensive. It's actually more useful to a Psi Operative than Psi Armour.

Seems to be a bug where, if you use a Medkit to heal a soldier with Poisoning, all soldiers with Poisoning have the Poisoned state cleared, not just the one who was healed.

 

Unless Poisoning just stops by itself sometimes and this was a random coincidence?