Inspired by this thread, fellow GCA'er Matt Schmidt and I played a one-club match this afternoon to try and test the one-club vs one-club-plus-putter theory.
We used, respectively, a six iron and a seven iron and didn't miss the putter one bit. The worst results over the nine-hole match were a few three-putts from the 30+ foot range which, on these greens, could have easily happened with a regular putter. And we did this on a Doak course with pretty severe greens.
Less comfortable than putting were, in my view, the half-shots into some of the greens. I would note that we were following local custom with the player holding honors choosing the teeing ground (which sometimes did not mean a proper tee box), and thus appropriately choosing distances that put the other person at a disadvantage. But that said, I still found a 40-yard flop far more frightening than a 20 foot putt.
In any case, one-club on a firm and fast course is a blast and I should think that such an event at OM or any of the Bandon courses would be well received.