Since I got my pilot bag back in 2003, I always had some sort of trouble fitting everything I need in there. Granted, I carry lots of stuff, but it's all mostly useful. Some may roll their eyes at that since I probably have four or five flashlights in there, but there's a lot to carry. Just off the top of my head, I know there's an iPad, a kneeboard, a notepad, an E6B, a plotter, a sectional chart, a terminal area chart, instrument approach procedures, the ContourGPS, the ContourROAM, accessories and mounts for the two cameras, a Garmin GLO, and the assorted flashlights. I'll admit, for a bag that was aimed at the student pilot, it holds its own, but I've outgrown it.
There are certainly other, larger bags available from places like Sporty's, but I figured I'd break the mold slightly. I ended up getting a Timbuk2 messenger bag because they can haul all kinds of things, and are versatile enough to carry what I need for flights. All of the extras pilot bag makers wouldn't really think of (the cameras and other electronics) fit with ease, as well. The bag I actually ordered is a large custom laptop messenger, which means it has a padded sleeve built in for a laptop, in addition to a padded pocket for an iPad. You can see it near the back with a red lining in the picture. That will fit my 17" laptop, and the iPad is in front of that. Beyond that, there's a cavernous space to put whatever else you need in there, with a few other pockets to organize various other things like pens, phones, and keys.
On the two flights I've taken it on, it's proven a lot easier to work with. It's not standard by any means, but it certainly fits everything I need it to with ease. If you're looking for a bag, it might be worth a look if you're not bent on buying an actual pilot bag. Most of the bags are customizable, as well, so you can change the colors, and comfort options to fit your personal taste. I can definitely say it's a lot more comfortable to lug around.
I'd say that spread speaks for itself.