Comment by daemin

It was used extensively at a former workplace of mine where each class that wasn't a message or data type was a pimpl. They had implemented their own private pointer class to handle it. It worked well enough to avoid pulling in lots of headers, but was still a PITA when you wanted to change methods as you'd always need to change the method signature in at least 3 places - header file declaration, source file definition, source file impl definition.