Manual controls are peculiar or unusable, auto focus is non-existent, and its 1280 x 720 maximum picture quality just doesn't cut it when compared to a dedicated HD camcorder. Recording videos for extended intervals also caused the D90 to run into overheating issues—prompting a swift shutdown of video mode.
They did like the 24p mode for it's cinematic look, and they found that the low-light performance was reasonably good - though they had been expecting better - but in general they weren't impressed by it as a video camera.
The 24 fps shutter speed does create a unique look, and it has a more cinematic feel than the 24P mode some camcorders offer. However, the D90 has way too many problems with video performance—choppy auto exposure, no auto focus, rolling shutter (producing wobble), artifacting, moiré patterns, and lack of sharpness with images of fine detail.
Also troubling was the five minute clip limit (note that the Canon 5D Mark II limit is about 12 minutes.) They also found that after about 30 minutes of continuous use the sensor would overheat and the camera would shut off live-view mode. They then had to wait about 15 minutes before using it again.