I thought I should post this now, have used my Lowepro M-Trekker HP120 alot when biking. It is well suited for that actually. Yesterday I was on a MTB ride that offered various conditions, some exciting ruffy parts and some lower paced. It sits very good. If you have the right belt tension you can just swing it around to access the camera and grab a shot and then swing it back, and it even sits good when riding.
Here on pic combined with a smaller backpack (a bigger normal sized is not good because they interfere). I have started to use he PL 8-18 alot and I had that lens on the E-M5, without hood. And you can still fit a smaller lens like the small 35-100 or even the 40-150R beside.
One very nice feature is you can use it with the belt (actually an optional purchase), or the shoulder strap (included) or both. Another feature is a rain cover hidden in a zippered pocket on the bottom of the bag. The cover is tethered so you can't lose it. The belt has enough hooks that some other Think Tank accessories can be mounted since the bag is so small.
Currently, it's the only bag I own. I can fit my E-M10 with lens mounted, plus one of two more lenses, spare battery, filters and some other small items. On a bike trip from the US to Canada, I was able to get my passport, wallet, maps, keys and snack bars in there.