I bought the iPad Camera Connection Kit because I'd heard it allowed you to connect a regular USB keyboard to the iPad, as well as USB microphones. Also, I was curious what support there was for video cameras.
I ordered the Kit from Apple ($29) as it wasn't available anywhere else. The quoted deliver was 2-3 weeks, though it arrived in about a week and a half. The Kit has two parts; a USB connector and an SD card connector. So far I've used the SD card reader (the USB experiments are next!)
I'm not going to focus on still camera support (there are other reviews that go into this at length) though I will say that my experiment with an 8mp camera with JPEG images went very smoothly.
The still camera I used - a three year-old Canon PowerShot - shoots 640 x 480 video. The iPad Photo application recognized the video, and let me select it and import it. I could also play the video without trouble, and move back and forth within a clip very easily: clicking on the timeline at the top of the video for an extended period expands the timeline to give you frame-by-frame accuracy to move forward and backward. But I could find no way to trim the video, though I could email the video to someone. [NOTE: I realize now I have to test again and see if you can trim before importing the clip]
So, the video on the still camera worked fine, but the iPad didn't recognize the card from an AVCHD camcorder. The iPad only supports 720p at 30 frames per second, which means that I can't use the iPad to play back video HD from the Canon 7D, which can do 720p, but only at 60 frames per second.
Reports of success with video cameras really seems to depend on the video formats used. For example, at least one user reports that the iPad doesn't recognize their Flip video.
There's already at least one video editing application for the iPhone, so there will probably be something for the iPad soon too (or you could probably use the iPhone app.) But if the iPad doesn't recognize the file formats to begin with - or even the files on the cards themselves - how are you going to get the files into the iPad to edit them anyway?