The things I would watch out for:
They probably use local contractors for installation. The quality of work probably varies somewhat. The warranty and service agreement that they include might mitigate this somewhat but I would read the fine print on those to be sure they are all inclusive. Also, since they are working on your roof, you should check the terms for what happens if they cause damage to the existing structure and cause roof leaks or other damage during installation.
This lease purchase thing is not unusual in the energy conservation business. Most of the multimillion dollar projects I have been working on have similar terms. 10 years is not a bad lease time considering the upfront costs but you need to have something saying what the buyout is at the end of the lease. Ours are usually a dollar.
Obviously, the lease might be a problem if you want to sell your house before the term expires.
It would probably be good to check with the local utility about the net metering thing. I am not sure that all utility companies are set up for that. Also, there are probably incentives that you would qualify for.
That's all I can think of for now. I sent the link to my work email and I will check around in the business to see if anyone has heard of these folks.