Right. Your Intuos Art Medium is their hoobyist level product.
The main difference between the Intuos and the Intuos Pro is the pressure levels.
Your current model has 512 pressure levels, as did my old Bamboo. I could certainly tell the difference between 512 and 2048, but I can't comment on the 8192, because I have the previous Intuos Pro model (#2 in the list above). Going by the reviews though, the just released one has some issues.
Intuos pro also has 8 programmable buttons, plus 4 switchable modes for wheel-less rotation pad. I use the keys fairly often, and the rotation thumb pad is nice to have for canvas rotation. I've never used an Intuos Art, but it looks like these are missing.
If I had the choice, I'd buy the same thing again, and in Medium. My bamboo was small and it was just frustrating on a 27" screen.
There is one other alternative, there are a fair few tablets with screens in them now, some of them around the price of the Intuos Pro medium. Maybe that'd be more to your liking. I can't comment though, because I don't have one.