BPDU guard is a good idea on user ports.
It will prevent users from connecting their own unathorised switches to the network.
It also blocks a port in a case of a loop created by a user connecting his repeater to two switch ports, e.g.
UDLD guard is not very useful. It can help to detect wrong cable connections in a large switch-to-switch matrix. But the convergence is very slow - STP itself is much faster.
Regards,
Milan
