There are so many threads asking how easy it is to carry the 15" around. Maybe 15" rMBP owners can chime in on how the 15" is when it comes to actually using the device? Because while there is no problem with the weight of the 15-inch, some people need to consider how they will be using the laptop in the first place. Have you used it on an airplane? A train? A coffee shop? Other tight spaces? I just thought this could be helpful to those undecided between the two sizes. Because sure, carrying around the 15" is easy, but how the 13" and 15" are in terms of usability are really different.