I don't have them on the ceiling, but I do have about 15 of them right at the top of the wall next to the ceiling, about 4' apart. Never had a problem with them and glad I had it done. It doesn't help with your situation though of needing them for a middle row. But still, I would have no hesitation on putting them on the ceiling.

You can see some pics (of the old set up of my game room) here (was focused more on the games than electrical outlets, but you can still get the idea):
http://www.missilecommand.net/Joe_Bachmann_FTP_2015_09_15/unknown_comic_game_room/tour_view/
Some of the pics there show them a little better than others...
http://www.missilecommand.net/Joe_Bachmann_FTP_2015_09_15/unknown_comic_game_room/tour_view/01enter.jpg
http://www.missilecommand.net/Joe_Bachmann_FTP_2015_09_15/unknown_comic_game_room/tour_view/04move_right_1.jpg
http://www.missilecommand.net/Joe_Bachmann_FTP_2015_09_15/unknown_comic_game_room/tour_view/07move_right_4.jpg
http://www.missilecommand.net/Joe_Bachmann_FTP_2015_09_15/unknown_comic_game_room/tour_view/10move_right_7.jpg

Best of luck!

Joe