The following is based on my experience with re-roofing my house:
Initial service from the salesperson seems good and they seem really accommodating and eager to please and say anything to make you happy to sign the quote on the spot (which is a contract).
After you have signed up you then get a phone call a few days / a week or so later telling you all the things the contract does not include (even though in my case the salesperson verbally told me these things were included - eg scaffolding, down pipes, underlay), and that there is no guarantee or warranty on certain materials. These things cost (a lot!) extra.