The cable supplied with the HTC Desire is quite short, and is part of the AC charger, which I like to leave plugged in, so I don't have to fiddle around underneath my bed every time I want to transfer files between my computer and my phone.
Also because the one supplied with the HTC Desire is quite short, it only just stretches to my bedside table, so a longer cable would be better.
For these reasons I bought this product which has the length I need for the AC adapter, and leaves me with the HTC stock USB cable to transfer files.
Brilliant cable, seems nice and rugged too without limiting flexibility.