Thule Strävan for 15" MBP + Incase Tensaerlite for 13" rMBP
I've finally found the best way to carry my new 13" rMBP and iPad Mini Retina. I needed a professional looking backpack that I could use for daily office work without my laptop (I can't bring electronic devices where I work) to carry a few folders, Moleskin planner, etc., but also be usable when I travel and carry my laptop, iPad and accessories. Here are some links to them:
https://www.goincase.com/shop/sleeves/icon-sleeve-mb-retina-13/
http://store.apple.com/us/product/HFDR2ZM/A/thule-stravan-backpack-for-macbook-pro
They were a little pricey $99 for the backpack and $69 for the sleeve, but they work together perfect. The sleeve is the thinnest one that perfectly fits the 13"rMBP with the most protection. It is perfect for carrying your laptop to the hotel lobby, Starbucks, etc. when you don't need a lot of accessories (i.e. Charger, portable HD, etc) and still have some good protection. The laptop with sleeve fits in the laptop compartment of the Strävan backpack for additional protection. The backpack will protect the laptop perfectly fine without the sleeve, but since it can support up to a 15"rMBP the fit is perfect with the sleeve. In the same thin compartment at the back of the backpack you can also put a full sized iPad or in my case a iPad Mini.
There is an expandable compartment for all of your folders; hard "safe zone" for your sunglasses, iPhone, etc.; another compartment with pockets and zippers for your chargers, external HD, lightning cables, etc.; and water bottle sleeves on both sides. The bonus is that this bag is small to medium size and very "clean" looking. Not a lot of straps hanging around.
Even though this is a "laptop" backpack, there is a lot of room for "stuff" and not a lot of wasted space in the laptop compartment if there is not a laptop in it. I also like the fact that it doesn't look like a hikers backpack and you could probably carry it with a suit on.
The sleeve is just bonus protection because the laptop compartment is definitely adequately padded. It gives you the option of leaving your backpack behind and still have protection for your $1000+ investment.
Hope this helps anyone looking for similar options.