The GH2 with the latest firmware update (which includes a higher bit rate video capture, 1080p, 25fps, 24-bit) makes lovely 1080p video that look really great, with excellent handling of movement. I have only watched this on a high-rez quadcore MacBook Pro screen.
I have seen tests which show the results of the even higher bit rate video that Vitaly's hacks allow, but I have not seen these shown on a pro. high rez video monitor, which is where I would expect to see any difference. Most people frequenting user's groups have not ever seen video on one of these expensive monitors and are commenting on YT or Vimeo conversions of the cameras' outputs and in my experience, you really can't make a judgement about what you're seeing using this method.
For any work that will end up on a standard definition DVD (like my current work) 720p video is superb: we shoot in this format, edit in Apple ProRes 422, and down-convert and standards-convert the edited program from 720p to SD NTSC for the final DVD duplication.
If you are planning lots of graphic effects post-production, or you are planning on converting your video to film at some point, then 1080p is preferable.
Re. lenses: the Oly 45/1.8 is excellent, and so is the 20/1.7 (we do not record sound using the GH2; we do second system). I have heard that the 12/2 Oly is excellent too, and those three lenses will do all that we currently need. hth, kl