Old thread, but still there's very little good info out there. I've never gotten the full features out of my Intuos Pro M (PTH-651) on my Ubuntu 14.04 laptop.
I've managed to get everything to work except for the eraser on the pen and also toggling modes. The LED's change when I press the center button, but it doesn't change the function of the device. Considering how expensive these things are, it's pretty disappointing.
To me, the worst thing is that I've never been able to assign keys using the System Settings>Wacom Tablet GUI. I bring up the menu to map keys, and nothing happens when I highlight a row and hold down a key. So I had to go the hard route, making a script using xsetwacom to launch on bootup.
I also created a launcher, because I found out that if the tablet isn't connected at boot, the script doesn't work. This also applies if I disconnect or reconnect it at any time.
Here's some helpful information for you guys on where to find the key mappings on your system and also a link on how to set things up manually should you need to do so. It was the only thing that worked for me.
The mappings for all supported tablets can be found in the /usr/share/libwacom/ directory.
There are text files in the main directory that use a *.tablet extension naming convention. The buttons for the Intuos Pro are designated with alphabetical labels where A=Button 1, B=Button 2, etc.
The subdirectory located in /usr/share/libwacom/layouts/ contains vector image files that display a graphical depictions of the tablets and the button assignments. These *.svg files should be opened with Inkscape or another application capable of displaying scalable vector graphics files.
Here's the link I found helpful in creating my script file: