I bought a knock off just for fun and to compare it to the real band that came with my Nike+. It's quite poor and not as comfortable. It looks almost identical but the material/quality lacks.
The comfort of the real thing is probably what I like most about it, so doesn't matter how cheap the knock-off is, I won't be buying.
On Saturday I did go into the Apple Store fully expecting to buy a black Milanese loop band for mine and I didn't. Maybe the lighting in the store was too harsh but certainly in the display case it didn't look as black as I was expecting...I did think perhaps I was looking at a silver one but there was one of them in there too and that was unmistakable.