Four and a half years, four mk7's, and I've found the parking brake to be pretty good all in all.
I've had the odd patch where it behaved strangely. A few times trying to manoeuvre out of tight spaces on steep hills it has played up and a couple of times trying to pull away from traffic lights it has decided it wasn't having any of it, yet the following day it always behaved flawlessly!
As Watts said, there's a current recall and it might help smooth things out. I had it done on my last service and it has been working very imperceptibly smoothly since.