Bah Brower ate my post
I havnt compared a 1D to a 350d and my 20d but my comparisons have shown slighly better responce noise wise but the colour's you get arnt nearly as good.
I try not to go over iso800 even when shooting indoors, with my local track that gets me down to 1/50th sec for the most part so you get very limited. The alternate is to edit the photos with some undersaturation and you dont notice the lack of vibrance as much.
Also since jimmy mentioned the iso50 on the 1D, like the iso3200 mode it is only an effective iso and not actually a real one. ISO3200 is an underexposed iso1600 pushed to 3200, iso50 is an overexposed iso100. The digital processing is what kills the colour, I assume that iso1600 on canon's have too much in-camera noise reduction killing the vibrance and sharpness.
To use iso3200 I would nearly always be shooting for B&W final output as the colours are usually horrible.