A few years ago I completely rebuilt my brakes which included, new
rotors, pads and hardware, rebuilt callipers, new wheel cylinders, new
hoses, new shoes and springs. The rear drums look like they were replace
by PO and the master cylinder was one year old so I left those alone.

What a difference in breaking, night and day.  I had no problem locking
up the brakes at slow speeds...I never tried it at high speed.  Before
the rebuild the brakes worked fine and passed our NB Motor vehicle
inspection...so they were up to snuff, but they did not instil too much
confidence and they did fade on the Cabot Trail...not fun.  The new
brakes tackled the Canadian rookies with no problems whatsoever.

I guess my conclusion is that the OE brakes, if in tip top shape, appear
adequate.  I just don't think they have a lot of safety margin when they
start to get a little tired.  A more "robust" brake system would likely
have a larger safety margin and therefore could still be adequate when
they get a little tired. 

Pascal
'84 Westy