I've just been sitting here for a while surfing the web. The only two apps I have open are Chrome and iTunes (which is idling), and after a while I started to notice it becoming ever-so-slightly annoyingly warm on my legs. I whipped out my IR thermometer and sweeped the bottom of the case. From back left to right it peaked at 104F and as I went away from the fan and other heat sources, dipped to as low as 97F by the time I got to far right. I probably wouldn't game, render in iMovie or iTunes with it on my lap, but am mildly surprised I noticed it as much as I did. This is far from a dealbreaker, though.