I too bought the HDC-HS9 from Amazon.com this week, with high expectations of it's 1080/24p performance, only to discover massive incompatibility issues with iMovie08.
Upon connection to OS X 10.5.2 through USB, iMovie properly detects the camera (both the HDD and the 16 GB SDHC card). The import screen even appears with thumbnails of all of the videos. However, there are two problems with the import that pretty much render using iMovie to edit the video impossible until either Apple or Panasonic (or both) correct the compatibility problems.
1) Video recorded in 1080/60i format cause both iMovie and Final Cut Pro to crash instantly on import, and display the "Send report to Apple" dialog. I cannot get a single 1080/60i video from the HDC-HS9 to import without crashing iMovie.
2) 1080/24p video imports just fine, but there is some incompatibility with iMovie's ability to playback 1080/24p format from the HDC-HS9. Imported videos play back at about 1.5 times the appropriate framerate, while the audio plays at normal speed. So it is like watching your video in fast forward while listening to it at normal speed.
I have had my eye on this camera since January, when it was first announced, as it is one of the first cameras on the market to use a hybrid combination of HDD and SDHC, and with it's price of under $900, the videos produced by the 3CCD Panasonic engine are incredible, even on my very large Mitsubishi 73" 1080p rear projection TV.
Unfortunately, upon experiencing the problems for the first time last night, I ended up scouring the web, apparently like every other HDC-HS9 / Mac owner, and found the following insightful postings.
Macrumors.com - where other HDC-HS9 owners are experiencing similar problems:
http://forums.macrumors.com/showthread.php?t=448228
Apple Tapeless camcorder compatibility list (HDC-HS9 is NOT on the list!):
http://support.apple.com/kb/HT1014
SimplyDV Review where problems importing to iMovie were encountered:
http://www.simplydv.co.uk/Reviews/panasonic_hdc-hs9.html
The camera did come with an eval copy of Pinnacle AVCHD Studio for Windows, which I guess I'll have to give a shot on my Vista desktop while I wait for Apple and Panasonic to correct this problem - which is highly aggravating after spending over $1,000 on HD camcorder gear!!!
Please let me know if you find a workaround.