If you mean the aft extended balconies; they are fantastic locations on the Spirit and probably every other Carnival ship. You can see in three directions; and there is almost no foot traffic in the corridor.
If you mean balconies in the rear third of the ship, they are good locations in that they are closer to the ship's only MDR, the Lido buffet, and the 24-hour pizza. If you are aft of the last elevator banks, there is a lot less foot traffic also.
Enjoy your cruise.
I am a Cruisaholic; "I'm Not Dead Yet"
Carnival Inspiration, January 17, 2014 Long Beach, CA *** Carnival Liberty, March 22, 2014, Miami, Florida *** Carnival Miracle, September 10, 2014, Seattle, WA *** Carnival Freedom, March 21, 2015, Fort Lauderdale, FL