My 3G, 3GS and iPhone 4 were all black, so I went with white for the 4S. I did it to have something different from my last three phones, and because I wanted it to look different than the 4 (mostly to "see something new" since a redesign didn't happen this time around). I think it's beautiful and it certainly stands out and everyone knows it's "the new" iPhone.
With that said, I think I'll go back to black the next time Apple launches a new phone. Not because I am dissatisfied with the white model, but being that everything in my home is either black, aluminum or chrome, the white iPhone just doesn't fit in with the overall theme. I know it sounds silly, but that's just my personal opinion and little stuff like that doesn't go unnoticed by me.