Just watched the video. The two people playing should have spent less time talking and more playing. Also, the stealth section shown in the video didn't seem too bad, but it's probably the first stealth section of the game. While it's no Deus Ex, I wasn't really expecting it to be. As for this whole Agrues stealth section complaint, it sounds like the people running into issues with it aren't keeping track of what their special abilities are. Granted, from the IGN video, we've seen that the mist works differently from LOS1's DLC. But still, if one was playing Deus Ex Human Revolution (which has better stealth sections than what was shown in the video), you still would be aware of the ability to turn invisible if you kept good track of what augmentations you have unlocked and which ones you haven't.
At least, that's how some of these reviewers complaining about the section come off to me, anyways. (especially if they are playing as bad as the people in that video, if not worse!)