I think the majority of godaddy domain purchasers are first time buyers or small businesses that do not know of other domain companies (especially considering godaddy's large advertisement investment).
I think many big time operators / hosting providers use them too because of the price, their inbound transfers are actually sold at a loss (when you take into account all the fees they have to pay).
Most other registrars that do larger volumes will sell you at about $1 over their cost.
I'm starting the process of moving from godaddy over the next week or two. Long overdue, but name reg is a "sticky" business which is why a boycott although a great idea will take consistent pushing.
After some review, it seems namecheap will be an acceptable route. One concern is the recent lawsuit lost by namecheap for private whois info. I hope this doesn't make them legally gun shy. Although the lawsuit results should effect all U.S. based registrars equally. Anyone have recent opinions on namecheap or any others?
Using moniker and very happy with them, not a single glitch since I started there when enom bought out bulkregister (and I decided to preemptively move out instead of waiting until enom and BR system integration).