I hate to admit it to y'all, but I went all CSI on a crappy sample video from the pre-production Panasonic GH1 to check out its jello-factor. Verdict: skew is present, but it's minimal, and hard to see without this kind of party-pooper hoop jumping.
The original video is here. Props to Slashgear for making a 720p version available for download.
Here's some 5D Mark II footage for (highly unscientific) comparison. I assume this has been run through some kind of auto-stablization such as one finds in Final Cut Pro and iMovie 09, which is not unlike what I did to the GH1 clip.