I just don't understand the fascination with thin (and LEDs). I have seen way to many ben and damaged phones ... I don't see the attraction that sacrificed thinness for battery life. I used to charge my Treo 650 (best smartphone I have ever owned) once a week. I dropped it when out running in the snow and found it by stepping on it 3 hours into my search ... was fine. I used it as my primary device for everything mobile for 6 years and no, never changed the battery.
With 6 smartphones in the household today, no one can get thru a single day. When replacing a cracked screen on one, thought might as well get a new battery and regretted not doing so as within 2 months it stared going shutting off at 35% battery life.
The lack of thermal problems and getting mobile GPU performance up close to that of desktops on notebooks is mostly attributed to the massive improvements in efficiency of nVidia's GPUs. The big problem with slim notebooks is, if you are going to use that GFX power, there is still no escaping what that power does to battery life. I still can't jump on the train in the suburbs and commute to NYC running AutoCAD w/o having a dead battery before I get there... and that's with a whopping huge battery that certainly won't fit in a slim line notebook.