3.9 supports the G12. The disk in the G12 box contains DPP 3.9.1, but no DPP manual - which I had to search for online. In the course of that search I also found the 3.9.2 update on the European Canon website, which I did right away.
Not sure what the differences are between 3.9.1 and 3.9.2, since I did the online upgrade within a day!
Ironically, DPP provides better support for the G12 than it does for my XTi, since the XTi doesn't record shooting distance, so the Lens aberration correction screen comes up with the shooting distance slider for the XTi at infinity, with a "<!>" notation meaning - I assume - "I have no idea what the shooting distance was."
It would be nice, however, if that slider gave you some indication what distance you are setting it to when you slide it!