In addition to the obvios winch, PTO could run a snowplow down pressure unit, a set of leveling jacks, any number of tools off the rear bumper, augers, tilt beds, steering assist, etc... They are really work truck options, but also something you can use to be much more awesome than the other guy. If I was dropping all the coin on a new truck, I would probably get the PTO if I knew it was available.
I would want to know exactly what you get in the PTO option though. If it is just an installation port on the transfer case, it might not be worth the money. If it a clutched, driven shaft, it is probably worth it, even if you never use it!