Counter rotating propellers

I've had a questions I'd like to foist upon the collective knowledge
here...

I have a few of those "World's Worst Airplane" books and enjoy reading
about the creations of those in the old days who were basically working
by the seat of their pants.

I've noticed that their were many planes during the prop-to-jet
transition years from about 45 to about 55 that used counter rotating
propellers. I'm wondering what the perceived advantage was?

Seems to me that the added complexity and cost would be a disadvantage.
It's pretty simple with one propeller: Take engine. Fasten propeller to
flange on front. Put on airplane, Fly into the wild blue yonder, All
those gears and driveline parts were mighty complex and, in my reading,
the added complexity was usually the thing that put the plane into the
'world's worst' catagory.

I notice that notable post war military aircraft such as the B-36 and
the C-130 (plus more) used one propeller per shaft. If there were an
advantage, you'd think you'd find 'em on a military plane. Yet, if my
reading is correct, the Soviet long-range Bear bomber had
counterrotating propellers.

So, that leaves me again with my initial question:

What advantages were being sought through the counter rotating
propeller and, if there were indeed advantages, why aren't they seen on
production propeller driven aircraft today?

raoul