We have taken 4 Disney cruises with 4 adults(DH, DW, 2DDs age 26 and 21) in cat 5/6 rooms and have had no problems. Rooms have always seemed larger than I expected before first cruise. DDs have no problem with the beds (converted sofa and pull down bunk). It really helps if you unpack everything and put it away immediately. Plenty of storage for the normal family. If you have lots of suitcases, try to get some that will fit inside of each other when empty. You should be able to get those in the closet out of the way.
The split bathroom really helps also. We give our DD's one and we take the other.
If anyone needs privacy to change, etc, the curtain between the bed and sofa area can be pulled, which is very convienent.
All in all, even though the cabins are small compared to most hotel rooms, the space is very useful and well designed. All you really loose is the extra walkspace you would have in a hotel between the end of the bed and the wall. With the veranda, all 4 of us like to spend lots of time in the room resting and we don't end up killing each other. To me the rooms are one of the high points on Disney.