I hate it and not only I think it is stupid, I think it's stupidly arrogant! Nevertheless, I've seen quite a bit project managers (even ones who are really bright) using this "naming convention" and add the "PMP" after their name.
The thing is becoming a joke, I've seen all kinds of (sometimes worthless) certifications being added to a project manager's name, why?
I wonder when someone who knows nothing about project management reads the following title:
"John Smith, PRINCE2" I think he'll be looking at John, with huh? Prince of what?
As for the benefits, I have to say (regrettably) that since suckers constitute the majority of the world, people tend to respect someone who adds PMP (or whatever) next to his name. They think he's a REAL project manager (while we all know that project management can be only gained by experience, and there are many inexperienced project managers who cheated their way to the PMP because of the lax control). Anyway, project managers have to be humble...
Having a project management certification is not rocket science people! You shouldn't put on your business card!