Haven't done business with them, but I've researched them.
I wouldn't sign a 20-year lease unless it was at the same time as I was signing a 20-year mortgage. I prefer to buy things upfront if at all possible. I don't even sign 3-year cell phone contracts, I use month-to-month.
I'm not very good at estimating my future plans. Last time I thought I'd only stay in a place for a year, it was six years. The one year I buy a conference pass months in advance to get the big discount, turns out to be the year I can't go.
Solar City seems to be enjoying success so far, so I guess they're finding people to take their terms. I just wonder what will happen in ten years when people are going delinquent.