Don't want to rain on your parade, but - seems about right to me. "Well lit room" is a very subjective term, and it looks like yours is lit by no more than a couple of tungsten bulbs, right? That's actually pretty low light, darker than being under a streetlight most probably.
You've got an F2.8 lens on your camera, which will probably require an ISO of around 1600 to be acceptable - much as you're seeing, and pretty noisy with all that H.264 compression. This is analogous to a fair bit of 'gain' in your video camera, but the 550D doesn't do such a good job of noise reduction.
Using Canon's own (dirt cheap) F1.8 50mm prime lens in a room with 3x60w light sources, I need to use ISO800 to get a decent exposure.
You can't use a cheap lens and get great results with something like the 550D - as excellent as it is. All the example videos you see on Vimeo are either shot with expensive, fast lenses, or focus on a light source, like a candle. A lit room, with areas of light and dark, is quite different...
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