It's basically the same system in teh C310's I flew. We'd go 90 minutes on the mains before draining the AUX tanks. This is even better, we had the nacelle tanks, but it was only on one side, so then you had to cross-feed to balance the load. Royal pain in the rear, but it was another 20 gallons you sometimes really wanted on board.
If you run the AUX's too early, you can over-fill the tanks and you'll basically just vent the fuel out, which does no one any good, and same thing with the nacelles. Overall, it's not as bad as one might assume, it'll just become second nature after awhile. Of course, when I was flying freight, we'd run the Aux's dry just to maximize our fuel usage, but not necessarily a good idea with Pax.