After years of backfeeding during blackouts (once not knowing we had power back for an hour after it returned) I finally got around to installing a transfer switch.
It cost about $200 and 6 hours work. Most of the time was spend getting the generator line across the house and into the transfer switch; the actual switch installation went pretty fast. Only problem was that 5 of the 6 circuits were on the side with the ground bus, which was full of wire already.