Used this today to aid a misjudged orbit by adding fuel to the lower stages by taking it from reserve tanks that were meant to be for the lunar lander. I haven't used it to trade between ships yet but I am planning a Mid-Planetary Fueling station for 0.17 that will be located in Kerbin orbit. Great mod, but I do think that fuel transfer should not be instant and rather be an overtime process. (e.g 20L/s with Rocket Fuel, 10L/s with RCS Fuel)