One thing that bugs me about Godaddy is that when they offer domains on "sale" - AKA, $10 .NETs, etc - you can't use a coupon on them. This actually makes the end price more expensive for those of us that frequently use coupons.
But, since GoDaddy must be Godaddy, they always offer upsells - if you have foo.net in your cart, they'll offer you foo.org for $4.99 (half the "discounted" price if you buy it outright.
So, you want foo.org? Put foo.net in your cart, take the upsell, then delete foo.net and keep foo.org for $4.99.