First, if you're buying domains you may find you don't have a choice. BuyDomains controls an awful lot of this business.
Second, if you can use someone else to buy your domain, ANYONE ELSE, do it. The service, if you can call it that, at BD is terrible. The young, obnoxious sales reps won't follow up or give you any service once you've paid for a domain. Their promise of 7-10 days turned into 3 weeks to infinity. They stink!
Keep in mind that even if the domain is registered anonymously, many registration privacy companies will automatically forward your email to the registered domain owner. So you can negotiate directly without these guys in the middle. They don't add value, just expense, hassle and frustration. Stay away!