I have never seen a case of "prior to" in which it couldn't have been perfectly well replaced with "before." Likewise, I've never seen "albeit" used where "though" wouldn't have been just as good. "Subsequently" can carry nuance that makes it useful, but generally I share Leeneia's objection to it. The objection isn't that they're not standard English, rather that they are used in order to make the user sound clever. In fact, they make the user sound pompous.