Video in DSLRs has a lot of potential. Larger sensors, interchangeable lenses, and so on. To me, it's all about a couple of things: shallow depth-of-field, and the ability to pull focus. The little clip below shows off my burgeoning focus pulling skills:
I've always found that consumer-grade video cameras do for video what point-and-shoots do for still photography — everything's in focus. I like the ability to blur the background to draw the eye to my subject.
You can see the background flicker when the glass is pulled away — the light changed, and the 5D Mark II made an adjustment. I should have locked the exposure before shooting. The Nikon D90 doesn't let you do that, so its videos tend to flicker like crazy.
It's important to remember that being a good videographer is just as hard, and takes just as much practice, as being a good still photographer. Just because DSLRs will be able to shoot video doesn't mean everyone's videos of their kids, pets, and whatever else will get any better. They may look better in some ways, but we shouldn't fool ourselves.
And right now, these are hardly suitable replacements for camcorders. Without the ability to track focus quickly and accurately, it's little more than a novelty. Just to take those simple videos above, I had to put the camera on a tripod and lock focus before starting the shot.
Image stabilization works with the 5D Mark II's video mode, but the grinding noise IS makes in my 28-135mm is very audible. It would be wise to take advantage of the 3.5mm mic input if you wanted to record audio. A shotgun condenser mic mounted on the hotshoe would do wonders, and besides, the bulit-in mic only records in mono.
I'm obviously no videographer, but I must admit, it's fun to try.