I don't know what changed between V21 stable and V1.0 regarding the LOS calculation, but the Aliens can now shoot through walls it seems..
So, I started a new game, got a report that local forces have downed a UFO and went for a mission. My soldier was behind some crates and couldn't see an alien standing behind a corner. On the next turn, alien had no problem seeing me and shot me, still behind the corner. Ok, I thought, let's say that standing there he can bend around the corner and shoot me. I bring another soldier to the same position as the alien moved one step further than the corner, behind the wall. But, on the next turn he just turned and shot me through the wall. To make matters worse, another alien, much further away in a house, shot my distant soldier through what had to be like two walls at least (a house wall damaged slightly and a concrete wall), not to mention that my soldier was also hidden behind some object. I was so shocked that I exited the game immediately and decided to go back to V21 stable where I had no issues (thus don't have a screenshot, sorry, but the map was some I didn't see before which looked like a freigh train station with some office building in the middle and some cargo wagons on the bottom right).
Could it be a map-related issue as I don't see any other threads with people complaining about LOS issues.
Sorry for not being able to provide any concrete proof of this issue. I guess the auto-save is there so I'll try again the same mission later.