Panasonic cameras don't correct Oly lenses, and vice versa, which kinda makes sense from a business perspective. Yes, you can do correction in LR/PS with Adobe's free lens profiler. Note that making your own profiles is a major PITA, but perhaps someone has made profiles for GH2+lens combo.
9-18mm is a stellar lens, but it would benefit from correction. Below uncorrected (since I haven't made profiles, yet) shot at wide(st?) setting with the 7-14mm.
Another option is to wait for the Olympus 12mm f/2.0
to be announced on June 30th - it's supposed to be really good. If that's the case I'll probably sell my 7-14 so that's another option for you
edit: and I was talking about the Panasonic 7-14mm above, not the Oly 9-18mm.