Or just... running stuff that kicks on the GPU? Running development tools (ios stuff, java stuff) would always kick things in to overdrive and send the fans whirring, and killing my battery. Yes, I'm often plugged in, but knowing that, if I need to be mobile, I'm going to get 2-3 hours... was a hard pill to swallow for $3700, when for 30%+ less I'd have a machine that lasted longer, had quieter keyboard, etc.
However, Apple has previously led the market in power optimizations. I'm not confident they'll do that this time.