That battery life is a really good trade-off for that hit in performance. I've gamed on an airplane, and it sucks when the battery starts running out. I can't play the latest game after 2 hours on battery. My 180W power brick will not work on the seat plug (though a 65W Dell power brick does, so it does make my battery last longer)
If the smart switcher works on 2d games or light indie games, I would love it. Once the battery starts hitting 50% and if I could switch to a game that doesn't need as much GPU power, that means I can game longer.
AMD also has a feature called Radeon Chill, and if you have a 144 Hz monitor, if you go above 144 Hz, the GPU will start saving power. This was nice when I had an overheating GPU