I don't really care where I sit. There are advantages and disadvatages everywhere.
Advantages:
Front: First off plane, near bathroom
Middle: more leg room if you sit in the emergency exit row, still plenty of room for carry on luggage in overhead compartment
Back: Carry-on luggage right by your seat, no one pushing behind you to get your luggage and get off plane, can sit in seat while waiting for the bathroom, get on plane first
Disadvantages:
Front: if you are claustophobic you could get sick staring at a wall, last on plane so you luggage is normally no where near your seat, get pushed as getting off plane
Middle: always seems like the screaming kids are in the middle, people push to get off while your trying to let the people in front of you out
Back: takes forever to get off plane, if engines are in back its VERY LOUD, get hit by stuff as stewardesses are trying to get pillows, blankets out of over head compartments