after years of using 12-13" laptops with great (sometimes hot swappable) battery life, i have found that screen real estate is more valuable as i have to work with multiple windows. the trade off is i now have < 5 hours of battery life (and this reduces every week with the battery’s age).
i now use a 15.6" screen laptop so it’s difficult to work if there’s no space (eg, some plane and train seats intrude into my seat back tray). i have shifted to doing some of my work on my blackberry and 10" tablet in such situations.
i usually work out of places with a power point, so i’m plugged in almost all the time. many cafes and libraries provide them.
my regret is not getting a laptop with a bigger screen years ago, when they started making them small (15.6" in the body of 14" laptop).
finally, a laptop without a battery can be annoying to work on. i have a small laptop with a bad battery which i removed (by opening the whole thing up as the battery is not meant to be replaced by users).
it’s now too light and flops around when my palms are not on it… it is now unused and left at home.