I wanted a crumpler bag originally for my computer but I just did not have the cash for it. It is true that if you spend a lot of money on a computer that you should get a good bag, however, in my case, I had a good bag already. I just needed a second bag for rain because my good bag is leather.
I saw this in office max and I got it for $40:
http://www.targus.com/us/product_details.asp?sku=CBT200
My iBook 12" fits well, but the space is better designed for a 15" PB, which is why I am posting here. The bag is nice. It has this shock absorber around the bottom and sides (for dropping, I guess), one flat pocket on the outside of the bag (on the back where it would be next to your body), an adjustable, padded sholder strap, the padded computer pocket with a velcro strap, a spacious pocket for other stuff, and then a really nice organization section. For a low end bag, it is suprisingly super and I am glad I found it. What I like is:
1) the padded computer pocket and the shock absorber
2) it has enough space to really stuff it if I HAD to, but is nicely slim for everyday use
3)the organizer pouch is really cool. It has a key clip and two well sized velcro pockets. On the other side it has one large pocket, three pencil/pen pockets, a small pocket, and a small padded pocket. Behind this is another"hidden" zipper pocket. There is also a trick zipper. When you have the main flap of the messanger bag down, there is a side ziper that lets you access the organizer pouch. I think the padded pocket is supposed to be used for a cell phone, but my cell phone fits better in the other small pocket and I use the padded pocket for my iPod. Easy access and great for headphones.
I am also going to get a Powersleevz eventually, so this set up is perfect (and half the cost).