Don't get me wrong, I LOVE having all the real estate to look at. I can run multiple windows and be editing a photo while posting on a forum at the same time on a completely different half of the screen. It's great and all, but..... What a pain it is to try and take it anywhere! The 17" Mac is the most fragile because the large screen flex's the most and is easier to break so you are always walking on eggshells trying not to break it. It fit's fine inside a Kenneth Cole smoked aluminum hard case I bought for it, but I still have to lug a briefcase around with it in there. It's the perfect laptop.......... to leave at home. On the flip side, I have a white 12" Ibook that goes everywhere I do. Thanks to target disk mode, It's no different from taking the 17" The 15" was going to be my next purchase, but you just don't need a 15" if you have a 17" at home and a 12" for the road. if you only had one, I'd likely say the 15" is a compromise that works. What size do you guy's use, and if the one you have is not the one you wish you had, what size would you prefer and why?