I use a PCR-800 it's predecessor so very similar.
I use mine mainly for transport control of Sonar while I'm at the PCR (it's too far to reach to my desk

) but it will do full bank control of tracks and lots more besides. I have a couple of buttons set up for undo, redo, save etc so I can keep doing takes until
the PCR I get it right.
I also have a control map set to map the pads to drums so that I can play drums with it, both to my hardware drums and soft synths within Sonar.
I have another map that gives me control over my sonic cell hardware synth as well - for patch changing mainly - but also for channel control in performance mode and parameter control. I'm even starting to use it live as well, which for a guitarist is radical stuff.
It's very versatile without a doubt.