I disagree with your criteria to hire a painter. A prompt returned call is nice but does not indicate the quality or fairness of the painter. As far as a written estimate, that should be more of a qualifier for the bid versus an evaluation criterion. I'm not sure one would have favorable results by hiring a painter on this basis. As far as the bidding process, change orders should ONLY be used if the customer requests additional scope (PMP 101). Angie's list should consider asking reviewers if/how much they were told to pay compared with the estimate. Unfortunately, there are a lot of contractors that are unethical and need to be accountable.
Your painting contractor should be able to tell you which premium products they use, and why. High-end materials and products perform better, look nicer, and last longer - if your contractor uses low-end options to drive your cost down, they’re not doing you any favors. When reviewing your proposal make sure a specific product is listed, not just a paint manufacturer. Every manufacturer has contractor grade options. House Painting Parker Colorado