I've always said that since Adobe Lightroom hit version 3, one of the things it does best is Noise Reduction. Don't fear shooting photos in high ISOs if you really need to, you might be able to save it. One thing Lightroom 3 does well is to edit even compressed JPEG files in a somewhat non-destructive way. Just as an example, here's a test from a really bad video sample shot at F/5.6 ISO 6400 from the 5D Mark II. First placed the video file into Sony Vegas at the proper framerate, then exported to an image sequence of TIFF Files. Once I had all the TIFF files, I imported them into Lightroom 3 and ran the amazing Noise filter.
Once I ran the Noise Filter and color corrected just a bit, I then exported from Lightroom as JPEG files and threw them back into Sony Vegas (same framerate). Don't mind the flickering in the video, this was shot at the worst possible conditions under poor lighting and the TV on. Lightroom is so simple to use because after developing one image, you can apply the same settings across all the images at one time - we're talking thousands of images being batched process. Great for photos, and definitely not the ideal way to de-noise video files, but for you photographers you can see how well Lightroom 3 works.
Adobe Photoshop Lightroom 3