Bought this for my Wacom Bamboo Medium and it's a doddle to install and configure with extra panels in your tablet preferences to show the battery drain state and life left.
It's worth noting that you really do need to follow the instructions and do a FULL 100% USB charge of this before you disconnect your USB cable because the battery life really only reaches an optimum on a full charge and discharge cycle.
That said, because it's essentially powering a bluetooth device, you really aren't going to get super-long battery life out of this so keep a cable handy at all times.
No lag though, and really does free you up from a mess of cables if you're working on a decent-sized screen with a tablet cradled in your lap.