I recently bought a Cyan 620 as a secondary device to my 800.
Before entering the store and buying, I thought I'd go for the White 620, but after feeling it in my hands I didn't like it. The 620 is meant to be a cheap and cheerful handset but the white version is just cheap, and I imagine would get dirty fairly easily. I think it's to do with the texture of the shell - I think the white would work better with a more glossy shell like the yellow 920. If you get a white 620 I'd recommend getting a 2nd shell as well.