I too am not a messenger bag girl, but now that I have a MCB, I wouldn't want to do without it. As backpack said, I have a collection of Little Swifts. I use them as my every day carry bag. The two have similar capacity, the Little Swift being larger than the MCB.
Most days a reach in bag is just what I want and need. I can easily see everything to find it without digging and having a panic moment. The pockets and O-rings aid in keeping me organized along with organizer pouches. The padded straps are comfortable and don't bind. The shape and style works in all kinds of settings.
I like the MCB when I need to have a larger range of motion and my hands need to be free. It's my day trip bag when the kids and I are going to a park or museum. Sometimes I use it with travel.
I too want an Aeronaut, and was for sure I was going to get Aubergine/wasabi. Now, I'm intrigued by Nordic. I wish there was a Nordic/Wasabi combination, but that would make my decision even harder.