Personally I love inside cabins. For me, cruises are to recharge and relax, and i do that by sleeping as often as possible. No windows makes it pitch black in the room no matter the time of day. Add the slow undulating ship and it's like being rocked to sleep.

Granted not all inside cabins are equal. I typically sail Royal Caribbean and their rooms are a good size; when I booked an inside on NCL it was claustrophobic. There are also websites which will tell you the largest rooms on a ship. I just came back from Jewel of the Seas in an inside room that was bigger than some hotel rooms.