Company originally requested a full prepayment, but settled for getting paid $1000 after delivering materials onto my roof and backyard, and getting paid the balance after finishing the job.
Job was done reasonably quickly.
There was one occurrence of using old material instead of new (one sheet of plywood).
One piece of flashing get blown out within a month or two after the job was finished (incorrectly fastened), got repaired after one call to the company without any fuss or additional costs.
Funny: Company was somewhat reluctant in providing references of previous jobs. The persons they eventually provided were hard to communicate with (inadequate English).