I just got a new job, and found myself needing a laptop bag that is more professional-looking than my Timbuk2 backpack. I agonized over the choice between the Zephyr and the Empire Builder. But from everything I read here and elsewhere, it sounded as if the Zephyr is huge and the EB is extra-huge.
Ultimately I chose the Zephyr (used from eBay since they're not available new since last August). It's big enough, I think, but it's not that huge. I have it pretty full, and that's with a MacBook Air in a neoprene sleeve; if you had a 15" laptop in a Brain Cell I don't think there would be a lot of room left for anything else.
On the plus side, I did get everything in it, and it's pretty heavy. If I'd gone with the EB, I surely would've loaded it up even more and made it even heavier.
Anyway, I just wanted anyone making the same choice to know that these bags aren't as enormous as my reading led me to believe. I'm still not sure I made the right decision, but I'll give it a little time. I can always try for a bag swap with someone who got an EB and finds it too big, or just resell the Z and buy an EB new.
Not that this advice matters too much, since again, the Zephyr isn't available new at this time. I wonder, is it ever coming back?