Not working for me here either...
I have an older tablet, the GD-1212-U (USB), and I was using it successfully with the older MacBook (10.7.5). The driver I was using was version 6.1.5-2.
When I upgraded to a Mac Mini, I had some luck with the tablet, even occasional use of the preference pane to set it up. With two 24" screens connected, I had the tablet limited to one in order to maintain ratio.
Then I updated the OS to Yosemite, and all has gone downhill. If a driver is installed, I do have pen access. One screen has to be off in order to keep the ratio to one. The pref pane won't open. I've tried installing other versions of drivers, with no luck (either it won't open or it's a mismatch).
Ultimately, I'm looking to go up to a Cintiq eventually, when the pennies roll in... I hope I don't have to deal with similar issues at that time. In the meantime, the old tablet is still hooked up to the old MacBook, a secondary machine just for that sort of work.