Yes, generally speaking Nikon's awful. Basically there's 2 cameras to even think about considering for anything vaguely serious when it comes to Nikon and video. The D3s (for a 720p camera, it's ridiculously good, and the noise is a lot more "grain" looking than the obvious digital noise of the Canons and has a live histogram). But, it's 720p, and the D7000 (which would be awesome if not for the fact it ONLY shoots 24fps @ 1080p).
This is one of Joe McNally's early D3s video experiments shortly after he upgraded his pair of D3 bodies.
[youtube]EvWnMb5XRp0[/youtube]
The D7000 is great if all you're interested in is shooting 1080 @ 24fps, but with Technicolor's recent Canon colour profile release, D7000 owners will have some catching up to do to figure out the best colour settings to use to maximise dynamic range. But, the footage from it is beautiful, the rolling shutter issues are minimal (relatively speaking), it'll record for up to 20 minutes at a time (longer than the Canon's 12 minutes), and with the tests I was doing (outdoors in typical British weather) it didn't give us any hassle about overheating. The D7000 also has persistent HDMI output while recording (something you don't get with the Canons until you're at least at 7D level - I'm not sure about the D5100, I haven't had one to test).
The D5100 was looking like it could actually rock Canon's world, but they failed to provide full manual control over ISO & shutter speed while shooting video (come on Nikon, what the hell were you thinking? people buy SLRs specifically for that manual control!). The quality from it's great, and (maybe I'm biased) overall better looking to me than the Canon (but bear in mind this is bleeding edge vs. 2-3 year old commercial technology now).
So, Canon still wins in many respects. Between the D3s, D7000 and D5100 Nikon could produce an outstanding HDSLR that would be better for video than any Canon, imho, but they've failed at every point to put everything into a single body (and they still don't have a body that does 720p @ 60fps that even Canons like the now obsolete 550D can do).
The D300s, D90 and others that only shoot 720p fully auto (or only manual control over the aperture) are useless. You can't get any kind of exposure consistency from shot to shot without some serious pre-planning and messing around each time you hit the shutter, and even then it's mostly luck.
However, for more family type stuff, where you want a DSLR to replace budget camcorder, don't want to have to think about anything, and just want a "do it all for me" point n' shoot video camera, the D5100 is about as close as they get at the moment - it seems they specifically designed it to compete against the low budget camcorders. But again, this is the latest HDSLR tech to hit the shops, so that could change in a few months.
All I want is a Nikon that lets me do 1080p @ 24/25/30fps, 720p @ 24/25/30/50/60fps, has a live histogram, and gives me full manual control over aperture, ISO and shutter speed, and HDMI output while recording. That's not too much to ask considering Canon owners have had that for a good couple of years now. Now, if only Nikon could get all those features in a single body, I'll be happy.
If that's not in the eventual D400 release (I like my crop sensors, closest size to 35mm movie film), then I'll probably stick to my D300s for stills permanently, and start collecting Canons for video until I can afford an FS100 or F3.