x11-drivers/xf86-input-wacom-0.13.0 has recently been released. It adds "tap-and-drag" support for touch-enabled tablets. Reproducible: Always Tried bumping the version number on the 0.11.1 ebuild and the driver has been running fine on my ~amd64 system.
This is now in the main tree, please let me know if you run into any problems with it...