Bag recommendation for OM-D

You need to examine how you will actually carry your gear. Don't think of a bag as holding just your camera gear. Think of what you actually carry with you and how you'll be carrying it.

For example, when I go on a trip (vacation or business), I only bring a single messenger bag with me while I'm out and about. It has to do everything, carrying my camera, paper maps, guide books, water bottle, small first aid kit, Advil, headphones, iPhone charger, etc. And it has to still be small/light enough for me to shoulder it all day long, for 16 hours if need be.

My choice was a CourierWare mini messenger bag, which holds everything I need (it gets stuffed full for airline travel, and emptied half out for daily use), except for the 16oz water bottle, which I carabiner onto the shoulder strap.