I've been through the 1.1 specification and I see that I'm still lacking one feature : how to print/get a message describing (even tersly) the last error. The models could be based on the perror()/strerror() calls (clPError() / clStrError()).
I had to duplicate the cl.h section about error codes to build the appropriate strings to issue human readable messages. I wish it was provided as a standard (mandatory) function so that whatever the implementation is (or will be), we can get the actual message.
This is important for high quality production codes.