For the case Peter cites, yes, it does add clutter to the pathname to say "..metas" (actually, it is "...." now in the current reiser4, not "..metas"). This is because you aren't looking for metafile information, you are looking for a subset and describing the subset, and that just requires a file-directory plugin that can handle the name of that subset and parse the file to find it.
The problem with the
cat /etc/passwd/..metas/contents/shell[username = "joe"]
syntax is that it doesn't really achieve namespace unification.