It arrived this afternoon and I'm actually really impressed. It feels very solid, the magnet holds well, the connectors to the watch are metal, and it has little play side to side (albeit more than the official strap). I've not tried running with it yet but have given it some good shakes and it doesn't seem to have loosened. I also tried scratching the inside of it quite hard with a set of keys, and it hasn't been discoloured or damaged at all. I'd feel marginally more secure with a genuine one but it feels very good quality and for the sake of the best part of £50 it's a better deal.
The branding is not prominent at all. It's barely visible in most lights, unless you're looking for it or really fussy about this kind of thing.
A couple of pics (excuse the absurdly hairy arms, please!)