They are selling some domains (subdomains to be exact), but at least they aren't trying to mask them like new.net and a few "alternate root" providers. I certainly woudn't buy them for resale or speculation, but if you really wanted one and it's better than what's currently available, I'd say go for it.
However, bear in mind that if you register domain.us.com, you may just find in a few years the more legitimate domain.com.us version available if the .us domain becomes saturated and they decide to use the now reserved com/net/org subs of .us.