In case Naim looks at this, we're looking for the most basic search functionality: the ability to get a list of all files.
The UPnP browse hierarchy isn't really useful in Media Center.
We import the tracks on the media server into our library so that all the goodness of Media Center browsing / organization is available in both Standard View and Theater View.
It might be possible to get the list of tracks by walking the browse tree instead of searching, but that's a crude solution in my opinion. Media server devices should offer at least basic search functionality.