Are you positive? I've seen ISO800 5D shots before, and this looks like you went RAW -> JPEG with CS3's defaults (minor chromatic noise reduction, zero luminescent noise reduction). This is what my 30D shots look like under the same circumstances. Either that or it looks like you shot all of these with a Nikon, which is all lumi-noise and no chroma-noise, due to in-camera forced filtering. Seriously, there should be a very minor amount of chromatic noise on these shots, even on a low-noise 5D. Double-check your CS3's RAW import defaults.
At any rate, very nice shots. 