I find the HQ spawn system particularly bad, where it often spawns both teams on the same side of the map opposite the HQ. Tactical insertions also seem to mess up the spawn points. I have been popped a few times and you see in the killcam your opponent's last death and his respawn from a tactical insertion right next to you. On the flip side I have had opponents respawn under my crosshairs right before my eyes in the same spot I just killed someone else. Nuketown is obviously a problem because of the size, but it's pretty bad on some of the other maps too.
The other thing that gets me is the difference in spawn distance between the two teams and the objective in demolition. Often one team basically spawns on top of the bomb and the other is in the furthest corner of the map. Gets annoying running the whole map just to find the opposition 'team-handed' and dug in.