They replaced our roof a few years ago and replaced the 2 skylights. When the job was done, they were very hard to get a hold off as they didn't replace the trim on the inside of the skylight opening where the drywall met the frame. The skylight themselves were installed on an angle that didn't match the opening.
Their warranty covered the skylight so when the skylights started leaking they found the problem but didn't want to fix it. After countless phone calls they said they didn't cover any damage due to the skylights' seals. We had Velux send us new seals but the roofers didn't want to replace them.
They show up fast enough.
The shingles were installed fast and that was relatively hassle free.
Overall, not the best customer service. You get what you pay for.