And they've finally got their video act together with 1080P video at 30, 25, 24 fps and using H.264 instead of Motion-JPEG.
But then they go and botch it up with odd functionality and limitations. The manual controls in video mode seem a little off. Andrew Reid of EOSHD tweeted "Confirmed no D5100 manual control in video mode," though DPReview clarrifies:
Shutter speed, aperture and ISO are usually set automatically, and you can press the AEL button during recording to lock the exposure. In the PAS modes you can apply exposure compensation up to +/-3 EV, either before or during filming. In A and M you can also control the aperture the camera uses for filming - although due to the bug described in our Live View section, not in the way you might think (or indeed the manual suggests).Nikon has always been a puzzle when it comes to video capabilities in their cameras. For ages, people have argued that Canon crimps the video capabilities of their still cameras because they have a pro-video division. But Nikon - who doesn't have a pro-video division to speak of - still manages to mess up the details!
The crucial point to remember is that the camera enters live view at the currently set (or metered) aperture, but then remains there no matter what changes you make, until you either exit live view or take a picture. This means, bizarrely, that movies aren't always recorded at the currently-set aperture.
Clearly Nikon needs help designing their cameras. No exposure meter (D7000). No manual control (D5100). Crazy. Why? Easy things!?
DxOMark: Nikon D5100
DPReview: Nikon D5100 Live View and Movie Mode