The current version of GIMP for Windows has a Wacom bug, if you're using the tablet to paint, you may find that the brush lags heavily.
The bug is identified in libcairo2.
To work around, you can install an older version of GIMP, copy out libcairo-2.dll, libpixman-1.0.dll and libpng15-15.dll and overwrite those in 2.8.14
Bug is here:
https://bugzilla.gnome.org/show_bug.cgi?id=736220
