Couple of new articles about mid-drives
OEM http://www.electricbike.com/2014-mid-drive/ Kits http://www.electricbike.com/mid-drive-kits/

Somewhat tempted by the Bafang BBS02 but struggling with the premium price compared with a Bafang hub. My other concerns are all about the sprocket freewheel and chainset. The DIY folks have had a lot of problems with reliability and lifespan of the freewheel. I'd be concerned about the possibility of getting something caught in the chain-sprocket. And I think none of them allow multiple front chain rings. Not necessarily an issue with an electric bike as long as you never have to pedal up a steep hill with a flat battery! Finally, there may be some problems getting a big enough front sprocket to get the gearing right.

Of the two cargo bike solutions the Urban Commuter looks much better engineered than the Stokemonkey. What this really needs though is a properly engineered solution from the OEM and probably built with a geared hub. That way it can be smaller, neater, and have a better final chain line. When it's built as a bolt on, the bottom right stay always seems to get in the way.