I was only dimly aware of D-handle routers until I found one in my Dad's garage a couple of months ago. It's an old Rockwell 150B and it came with an accessory base that has a roller on it; presumably to do bearing-guided routing with bits that do not have their own bearings. I haven't tried that feature yet. The bearing might be too old to operate smoothly.
The motor cap was missing; I bought a replacement from a guy named Dick Jarmon. The cap had only two of the required three semicircular recesses, which was as he said it would be. The original part is no longer made, but a PC cap almost fits. A cutting disc and then an abrasive drum on an electric die grinder made the third recess quickly enough.
I decided to try it out on a couple of operations I had to do on my project. I have to say that the D-Handle was very comfortable to work with. The ability to start and stop the router without letting go of it is a *very* nice feature. And I feel like I have a good stable grip on it too. On top of all that, it's one solid all-metal tool. I figure to use it regularly.