That's the way I always played it, Bagpuss. Incognito had me spooked, but I checked my book and there's no listed limit on quickdraws. Far as I'm concerned, this means that a 20th level fighter with two weapons, improved two weapon fighting and quickdraw can attack with six different weapons, dropping them as free actions between attacks.
Incognito: If you think that's overpowered, call it a number of quickdraws equal to dex modifier, or give it a second feat to make it unlimited. I think it's fine as is.