Initially I was slightly worried buying a 3rd party item, especially something as important to graphic/ audio quality as the cable. But, after getting it delivered this morning, my fears have been totally allayed.
The cable arrived nicely packaged, visually fitting in with other Xbox 360 gear, white with lots of green and curves. It looks good.
Construction of the item is excellent, no molding lines visible, nothing creaks when squeezed. The ‘Gold’ plated VGA plug goes in well, and screws up with no problems. It includes 2 x RCA cables for stereo / fake 5.1 (if you have the right adapter to convert from 2×rca to whatever input your speakers take.) In my case, I own a set of cheapie Logitech 5.1's, plugs in great, and feels like quality. This package also includes a separate optical cable, which is optional depending on your speaker / amp set up.
Obviously, as the actual 360 has not been released yet I cannot comment on the quality of the audio / visual side of things, but from reviews I have read elsewhere there is no difference between this cable and the MS HD VGA cable (apart from price, of course.)
All in all, why would you pay more for the 1st party MS option, when this 3rd party item will do just as great?