I recently received my Empire Builder replete with Brain Cell for my 15" Al PB, as well as the optional shoulder strap.
The bag is, to say the least, impressive. Every aspect of owning this bag has been a delight. Even the presentation of the bag as I opened the package oozed of quality and pride. The build quality is outstanding. Every clasp and zipper is extremely sturdy. There are more compartments than I'll ever possibly need.
The interior of the bag is perfect for what I use it for (I am a grad student and keep my PB, one 1000+ page textbook, as well as several notebooks in there at any given time).
To those that think that this bag might be too big, I would say to think again. I really don't think that it is too big at all. The last thing you want to do is invest money in a bag that can't carry all of the stuff that you need it to. If you spent upwards of $3000 (or even more ) on a PB it deserves one of these bags.
I would also encourage everyone to buy the brain cell and shoulder strap. With how heavy my bag gets the shoulder strap is a major asset. It is, by far, the nicest strap that I've seen.