This webcam is NOT HIGH DEFINITION (despite what the name alludes to). It is a 480p webcam. It has the utterly useless feature of resizing the image to be larger, presumably with the sole purpose of being able to advertise it as capable of doing higher resolutions.
Do a simple test: change the resolution as per the user guide and capture a still. Then capture a still at 640x480 and resize it to be larger using your favourite photo editor. You will observe that the resized 480p picture is exactly as sharp - or, should I say, exactly as blurry. There is absolutely no extra detail captured in the higher resolution modes. I'm using the latest drivers off the HueHD website.
It's even mediocre at being a 480p camera. The framerate is nice and smooth if the lighting is good. However the diagonals (eg contours of the face) are rather jagged in the 640x480 mode, leaving me to wonder whether perhaps it's actually upscaling from an even lower resolution. The jaggies are very noticeable and annoying. There is a large amount of noise in the shades of the face even in bright lighting.
People who rate it high must be comparing it to other really bad webcams. Objectively the picture quality doesn't deserve any more than 3 stars, and I'm deducting one star for the misleading name and another one for misleading specs.