Daniello,
I use a Brenthaven Pro bag for my 17" MBP. This bag was originally purchased for my 17" Powerbook, and I have continued to use it for the MBP. I do a lot of travelling by car in my job, and I am typically away from home several days every week.
The Pro bag provides plenty of space for everything else I need to carry along with my MBP. I end up stuffing it pretty much completely full, but I carry: A portable external drive, my digital camera, all (and I mean all) of the cables and adapters I might possibly need or want to use with the MBP, a card reader, a spare battery, my iPod, a pair of Bose QC2s, CDs and DVDs (blanks, games, data, etc.), my cell phone, etc.
This leaves me with the "extra" attache-style compartment of the bag for office type stuff: pens, pencils, printed material, important papers, etc. If I have something that needs to be carried, chances are there's a place for it in my Brenthaven bag.
The Brenthavens provide great protection for the MBP. I assume you have checked out the demos and specs on the Brenthaven website. If not, I recommend you do. I feel perfectly comfortable casually tossing the bag around, and my MBP is more than adequately protected. BTW, I never actually shut down my MBP; it is simply put to sleep when it is placed in the bag.
Now, with all the stuff I carry, the Brenthaven
does get quite heavy. However, it is no heavier than the instrument I must also carry with me wherever I go. For me, it simply provides a balance on the other side 😉 Someone else's mileage may vary. To be fair, most of the weight comes as a result of the additional items I carry with the MBP; with all that junk removed, the Brenthaven/MBP combo seems light to me.
So, what you get with the Brenthaven Pro bag is rockin' protection, combined with the consolidation that the design provides (meaning that it is intended to tote all of your other stuff just as much as it is intended for the MBP). I can and will attest that it works very well for this. If you are looking for a single solution to all of your cartage needs, Brenthaven is the way to go.
Scott