"I don't want to pay $100+ for an adaptor and I don't want one more thing to have to lug around with me (and possibly forget)."

I just bought an adapter (they call it a power inverter) that worked fine for my SFO-BKK business class flight - was only $29 - Micro Innovation 150W. Interestingly, the laptop I just bought (a Toshiba) allows me to trade off power consumption for performance. The highest performance setting kept causing the power outlet to turn off, but the other two settings always worked fine. Great for a 15+ hour trip. I loaded it up with 210Gb of movies, music videos and music, so I was set for the flight.
PS-the video system on the flight did not work...