I also vote for a DIY/conversion. I built a Surly Bridge Club with a 500w front hub conversion kit. It's a Grin Technologies RTR kit, SX front hub in a 27.5" Alex rim (rim brake compatible), 52v 14ahr (750w) downtube battery using 21700 cells, 30/55 amp Baserunner integrated controller, cadence PAS and twist throttle. The bike was bought new last fall and the kit applied shortly thereafter. Pricing was around $1100 USD for the bike and a similar amount for the kit ... so less than $2500 USD invested. The total weight without the fenders, winter tires and rear rack is around 45lbs and around 55lbs in it's full winter setup (including a pannier).

This bike is about as perfect a fun to ride urban commuter/grocery getter as I can build. The only thing I want to change is the gearing, I need more top end than a 32x11. It's quick and smooth (both throttle and PAS). The motor is protected from melt down by an internal temp sensor (the CA will roll back the power if the motor is pushed too hard and overheats). It handles all the different weather (icy, loose snow, rain, etc.) and still retains much of the rideability of the original non assisted bike. And to most folks it's just another bike.