I got mine for about 3 weeks now. Looks exactly the same as on day 1.
My gf got a white sports band which has become a little dirty, but I cleaned it yesterday with hand soap in running water - no problems whatsoever, looks like new.
I wear mine roughly 12 hours a day. My 5 month old enjoys using it as a teether. It still looks brand new. I just wipe it down occasionally with mild soap and water.
Same here... I've had my WSB since 4/24 and it's still bright white and looks new. I shower with the watch every day and that probably helps keep it clean. I think the worst that's happened to it was when I spent half a day at disney in 90 degree heat. I noticed some brown 'stains' on the inside of the band, which I think were a combination of sweat and dust. I rinsed it under warm water for a bit and they came right off.
I loaded/unloaded some heavy boxes and some blue coloring from the boxes transferred onto my hands and my white sport band. The band washed up at least as easily as my hands - just ordinary mild hand soap. It rarely needs any cleaning, but anything I've gotten on it has cleaned up easily.
Makes me wonder if the white iPhone case would clean up as well. I have shied away from it for fear it would always look grungy.
Lint from dark sleeves can collect in its crevices, of course; a tissue, not even soap and water, corrects that. For exercise, however, I revert to Black.
I've had my white band for 4 weeks now. It's been very easy to keep clean. I just use facial wipes every few days to wipe it down. It still looks as new as it did on day 1.