Knot - I bought that bag for my husband for his birthday last summer (he has the plain black and white one). He liked it for hauling fairly heavy loads and said it was stable if you cinched it up pretty good. He did say that it hurt his back unless he wore it pretty high up.

He also said that it was still sweaty...just in a different spot than a backpack.

I think a backpack with a mesh panel (that keeps the bulk of it off your back) would probably be the least sweaty.

Good luck with grad school!