This Video aims to prove of the existence of "native" ISO values. The theory says, that any other ISO value, rather than the native ones produce more noise and compression in the final image. There have been a lot of rumors around this topic and until now I have not found any comparison video.
So far it was not possible to dial ISO values in small steps on the 550D/T2i like on the 7d or 5d. It proves, that all other values rather than multiples of 160 seem to be interpolated and produce more visible compression.
It has to be kept in mind, that the effect has been vastly enhanced and real world differences might only be noticeable during heavy color grading