add to the mix: recent rumor about screen resolution increase coming for the 17" I decided this in an Apple store. I went and tried all 3, like Goldilocks. At the time I was torn between 15 / 17. One close look at the 17 and I knew it was too big (although if the resolution was higher maybe). The 12" became a big contender on seeing it, but there were too many little drawbacks... No lighted keyboard, no PC slot, fewer USB? I can't remember them all (it was a year ago but I may still have my comparison chart) The 15 was "just right" for me and I haven't regretted a moment of it. yes there are times a 12 or 17 would be nice, but 15 works for me for the most # of places I use it. You really need to see them and envision working with them in your likely environmens....