Read: they are not honoring them. When you enter a promo code, it does not say anywhere on the site or during the order process who that code is intended for. They will take your order, confirm it, give you a customer and order number, finalize the transaction, then a week later when you are expecting your radio they may (or may not...depends how they feel that day) email you and tell you they have decided to cancel your order. To be fair, I'm sure they don't do this with all codes and I'm sure they have honored some of them when they felt like it, but I just wouldn't count on it.
If you do order with a promo code I would suggest calling them and placing the order on the phone. Get the rep's name and employee ID# and any other info you want.
Anyways, back on topic, I tried ordering the startmate. The "promo" I used had either the starmate or sportster free if you sign up for at least 3 months. I liked the small size of the starmate, especially considering I already have XM. The sportster was just a little too big for the space I had. The mounting did concern me since it didn't really have too many options, but I figured I would figure something out once I had it.