I ran into a couple of bugs on my last mission. The first one is quite minor. I've found that if a guard is near a wall, when he is shot there is a chance he will fall through the wall. When this happens the game draws him hovering just outside the building.
The second bug is a bit more serious, I've managed to cause a game crash. After shooting the target, I left his office and took the elevator down to the first floor. As soon as the elevator doors opened I turned off power ot the building so that the guards wouldn't be able to use the elevator. As soon as I killed the power the game crashed with the following message:
An unhandled exception occurred at $0000000000636B2F :
EAccessViolation : Access violation
$0000000000636B2F
$0000000000518AF0
$000000000053E8E7
$000000000047B480
I'm running version 0.1.2 of the game on 64-bit Linux (Ubuntu 12.04). I've shut off power while standing in the elevator before (usually on the top floor) without triggering the bug. So this is a rare event.