It really depends on your budget. That $200 pays for your auto gratuities for the week. This means that your total cost of the cruise is less. We like to have an oceanview just for the light, but we have also done the inside to save the money.
I say that most of the time you are only in the cabin for sleeping and changing clothes/showering. It truly doesn't matter what type of cabin you are in. So if you are budget constrainded, don't fret about having an inside. Maybe you will get upgraded (unless you picked the cabin and did not reserve in a "to be assigned" cabin). If you picked the cabin when booking (which it sounds like you did) then you probably won't get upgraded.
Balconies and suites are nice, but not if it means you don't have that money to buy drinks or trinkets or go on an excursion....
Carnival Cruise Lines:
Fantasy 90, Celebration 95, Victory 05, Conquest 05, Spirit 6/06, Freedom 6/08, Holiday 7/08, Victory 6/09, Valor 9/09, Dream 6/10, Splendor 8/10,Conquest 8/11,Magic 11/11,Triumph 4/12,Spirit 7/12,Freedom 11/12, Triumph 2/13 - The fire cruise
NCL Dream October 2006, RCCL Mariner OTS June 2007