We've driven our MY over 4k miles so far, and except for road trips where Superchargers are an absolute necessity, all of our charging has been on the 120v mobile charger at home. We've not had an issue keeping the car at between 30-80% SOC, as we normally don't drive more than 20-40 miles/day. And once my wife picks the kids up in the afternoon from school, we tend not to go out again until the next morning, when we drive them to school. That means about 15 hrs of charging each day, which comes out to roughly 15-20% added SOC. And that's enough to keep the car charged.
If we install the wall charger, the quotes I've been getting are at least $2k plus the $450 for the unit itself. I'm not sure we will ever recoup the lost efficiency of 120V charging.