Issues with dslr's

Hi i'm a bit of a newb but i need i'm wanting to learn about dslr's that shoot in HD video and wish to learn

what are the issues? How do they compare to traditional camcorders?
What are the file formats? How edit friendly is the media produced? What about compression?

Any info would be greatly appreciated

The issues?

Well, the only ones with autofocus during video recording are the Sony SLT A-33 and A-55, and Nikons D3100 and D7000. The Sony's use the much faster and more accurate phase detect autofocus, and you can still use the viewfinder, which is an EVF, as well as the main LCD while recording video. As far as video recording goes, the Sony SLT's are the top dogs for the variety of reasons.

The SLT's use AVCHD video format. Which is very low compression format, that can also be a drawback by requiring heavy duty power in editing. Thats the biggest problem feedback I hear on that is that it requires much more power to edit than an H264 video file. I guess thats a double edged sword.

I don't know how they compare to traditional camcorders, I'm a photographer not a videographer :P... Anyway I'm not familiar enough with professional grade video equipment to compare it.

Anyway I hope that helps.