I've encountered a freezing issue on my PS3 and found info on on some other forums. Not sure if it effects other platforms. As far as I know this is how it goes:
- build the Gallop Chamber
- complete a mission
- scan for and begin another mission
- freeze during the short Skyranger landing scene
It seems to consistently happen on your second mission, that is if you haven't quit the game or loaded a save in between. That happens to be the quick fix. After your first mission, at the Geoscape make a save and load it, or load the autosave if it is turned on. I did that and finished the game fine. Again, it only begins happening after building the Gallop Chamber.
I've seen a few other minor bugs, but that's the only real issue at the moment. Waiting for a patch.