Hi Michael,
I have a couple of those bearing guides that came with various routers, but like Gary, have found them less than useful.
Not because they don't work, but because they have been largely superseded in usefulness.
What the manual does not tell you, is that the diameter of the router bit, must be smaller than the outer diameter of the bearing, otherwise what Gary experienced, will happen.
Also, the adjustment is critical. Viewed from below, the outer edge of the bearing must almost completely cover the router bit, except for the millimeter or so that you will be cutting (I will call it the width of the cut, to distinguish from the vertical depth of cut - which you may also be doing in steps). If you have to make a cut in several passes, this means quite a lot of fiddling.
Generally, the functionality has been taken over by bits with top or bottom bearings, that can follow the non-profiled part of a board edge. The only situation I can think of where such a guide might still be useful, is to cut a rebate (rabbet) all along the length of a curved board, with a straight bit. Even then, a rabbeting bit would be easier to use. [MENTION=20395]gmercer-48083,
Interestingly, I have such a two-point adapter as you suggest, on an old flea-powered B&D router. It is a piece of plastic that bolts on to the router base (same thermoplastic), and provides two points of contact with the board edge, one on either side of the bit. Have never used it either.