I think that having a GUID as a PK is an acceptable (didn't mention preferred) practice. Having it then clustered seems to make no sense whatsoever. I highly doubt that there are very many tables of GUID's that would have range queries ran against the GUIDs. (I'm sure there might be a few, but doubt that it's very often).

Like was mentioned before, use some other field for the clustered index. Possibly a field that is queried often and maybe even with range type queries.

David