Having studied the "bundle wrap" method of packing pioneered by onebag.com, I researched the hell out of carry-on bags that pushed the limits of the carry-on allowance of 45 linear inches.  However, Onebag recommends two very expensive bags that lack the excellent features of this one from eBags.  If I was to design a carry-on bag, this is what I would have come up with (minus the zip-out water bottle holder).

This bag, while not fully rectangular when loaded, uses every available cubic inch of the carry-on allowance.  There are no wheels or telescoping handles to eat up valuable space, and if you want to push your luck or check it in on the way home, you can expand the bag to fit 10% more stuff.  This thing looks big when packed but fits perfectly in the overhead bin.  So how much can it hold?  Here's what I packed in it recently, and I'm a tall guy: 2 pants, 3 long sleeve shirts, 4 t-shirts, 2 short sleeve shirts, rain jacket shell, hooded sweatshirt, 2 shorts, 2 bathing suits, 6 underwear, 7pr socks, pajama bottoms, some small hiking items, size 11 Vans and flip flops, snacks, travel paperwork, and probably a few more things I can't remember.

Keep in mind that this bag is all "function."  It's a backpack, and it can get heavy fully loaded.  If you want to look cute in the airport pulling a little wheeled suitcase, this isn't for you.  If you want to avoid checking a bag or stay hands-free and can manuever with this on your back, you won't be disappointed.

The bag is cleverly designed and offers a great deal of flexibility.  Check out the videos on the manufacturer's website, and consider purchasing an eBag shoe bag to use as the "core" of your bundle wrap and purchasing a 3-pack of small packing cubes to use in the top compartment to stay organized.  I look forward to using this bag again but it's not for everybody.