When i say they are more than worth it, i mean it. Of course everyone has different opinions, but wow i am specifically looking for aft rooms on our may cruise. We went on one in july and were assigned a deck 7 aft extended and we were skeptical; worried about seasickness, etc. Honestly, as strange as this may sound, i believe that staying in the back actually helped with motion (I think being in the back from start of the cruise, and during downtime tones down movement as opposed to being used to mid, and moving aft. I felt MINIMAL movement and i am prone to motion sickness
). I say take the leap and go for it. Only issue we slightly had was vibration but it was minimal and easy for us to get over.
edit: also we experienced minimal soot. We were worried about this as well, and saw almost none. The crew did a great cleaning job. And not to mention..
Castaway Cay views and any other port views are amazing. We feel that staying midship the view just isn't the same as being on the back with a "private" feeling view, all to yourself (not shared with the hundreds to the left and right, up and down)