Peter, I do'nt know about Sascha but to let you sleep sweetly let me tell you why I have, in one instance, been interested in reading the port latch. I were asked to find out why a unit sometimes behaved strangely and came to suspect that maybe the very dynamic input was occasionaly read low because somewhere in the customers code an accidential reset of the output bit happened. So I stuck in a catch for the port latch bit being low at read input time and eventually found the problem.
Sweet dreams,
Erik