Nowadays, the clay pipe is disappearing primarily for a few reasons:
They break easily, they get hot quickly, many can't pass a cleaner et. al.
However, of the clays I have, I find it useful to test new tobaccos instead of using a briar in my collection for fear of any dramatic ghosting. If you do end up getting a clay, be careful of the heat, and try and wet the stem portion with a bit of saliva so that it doesn't stick to your lips when you smoke a clay. Clays are cheap, and handy, and nostalgic.
Shutterbug