Unfortunately, in the temperature sense.
I've been running Ubuntu on my Mac Book for just a few hours now, and it's been consistently hot, even when it's not doing anything (such as a blank screen). On Mac OS this was very rare, but predictable. It only happened when doing something processor intensive (such as compiling). When I unplug the power cable, Ubuntu estimates about 2 hours of life, down from the five Mac OS promised (this one may just be different calculations though).
I imagine what the problem is is that Mac OS automatically adjusted the processor speed based on what you were doing. I understand HP laptops (maybe other brands?) do this manually, you can turn down the performance to get more battery life. If this is the case, Ubuntu isn't doing it. Is there anyway I can make it do this, or at worst manually change the speed?