The 20D files at high ISO are pretty clean, but at the expense of detail being smoothed over. Shooting a color swatch with no detail isn't an accurate comparison, which I remember seeing as well and thinking the same thing (20D was as good). I love my 20D, but I have come to realize how much detail is smoothed over. So, I only use it at 1600/3200 as a last resort and frame as tightly as I can to get as much details as possible.
Current: 5DM3, 6D, 8mm fish, 24-105/4IS, 35/2IS, 70-200/2.8IS, 85/1.8, 100-400/IS v1, lensbaby composer with edge 80, 580's and AB800's
Formerly: 80D, 7D, 300D, 5D, 5DM2, 20D, 50D, 1DM2, 17-55IS, 24-70/2.8, 28-135IS, 40/2.8, 50/1.8, 50/1.4, 70-200/4IS, 70-300IS, 70-200/2.8, 100 macro, 400/5.6, tammy 17-50 and 28-75, sigma 50 macro & 100-300