I ran into the AVCHD format for the first time last night. It was from a Sony Handycam with a hard drive recorder. AVCHD is one way of recording high definition video. The things I learned were:
1) AVCHD looks very good
2) AVCHD and Macs are not a happy combination.
This is not to say you can't edit AVCHD on a Mac, however it can be time consuming just to get the video on to your computer. Then it takes up about 5 times as much room as DV or HDV video that you would shoot with most other mini-dv tape camcorders.
Here's why. AVCHD is recorded in a format called H.264. This new format is a great combination of high definition and compression. The problem is editing H.264. To edit it on a mac, you need to change it into something else. Apple's two editing programs (iMovie 7 and Final Cut Pro 6.0.1) convert the AVCHD/H.264 video as it is imported. That can be a slow process. On my Macbook Pro it took 4 hours to import 1 hour of video.
That one hour of video was about 60 GB... which pretty much filled up my hard drive.
If you have an older power pc mac (instead of an intel mac), you can't use Final Cut Pro to import the video. It just won't do it.
On a windows machine, this is apparently not a problem.
But if you are editing on a mac, avoid getting a camera with the AVCHD format...at least until the technology gets better.