When I bought my new SR MB I wanted to get the most reasonable carrying / storage case (computer is home 99% of the time) and store the accessories with it. I ended up buying the incase bag with a flap and pockets ($59 @ Apple.com) and it's quite nice, olive fur inside. I'm glad I got this one instead of the one without the flap ...
But I wouldn't use this bag for a rough school environment. In that case, I would hop over to Microcenter.com and get the moshi codex sleeve; it was clear from all the research that the moshi codex was the best protection for the money, and it lets one work with the computer in the sleeve without having to take it out. There's a very good review on it out there, too. The reviewer comments on some translucent strips that hold the case to the screen portion that passes just below the isight camera ...
Some people swear by the Zeroshock, but I thought their foam was more cheesy than the viscotex used in the codex. $20 is not an unreasonable upgrade for protecting a $1200 computer.
And there's always Tom Bihn, but his bags have tags labeling Bush an idiot (they claim it's referencing Tom Bihn, but we know better, right?) I was considering the braincase but, shoot, what a lame tag that kind of sh*t just pisses me off. In all, aren't we sufficiently indebted to our Gov't for preventing all the terrorist attacks that would have probably hit us if it wasn't for the hard-nosed planning? So what my descendants are gonna help pay for a $2 trillion war, at least they'll be able to!
Good luck on your hunt! I think the incase nylon cases are nice, and the one I got will suffice for my needs .. we are all slaves to our macbooks and the more ardently they are worshipped and babied the better they will behave for us.