Hi Mike,
>GUIDs are bigger than integers and are not the fastest choice.
That's what we mostly use, too. Aside from making it easier on the middle-tier or client side to deal with new keys, GUIDs also have the advantage of supporting replication and disconnected scenarios. They are also more scalable because you don't need obtain a lock on a resource that increments a key, whether the resource is a SEQUENCE, an AutoInc field, a stored procedure, or whatever.
--
Christof