I also own a construction company and in the past I have dealt with them for roofing and siding due to hail damage, one company in particular was so rude to me on the phone I couldnt believe it. That particular job the homeowner told the insurance adjuster they would only be happy if I did the job, I told the insurance adjuster that I would only be happy if I got more money...in the end nobody was happy, I didnt do the job and the insurance adjuster still was a jerk. Since that experience I avoid insurance adjusters and Allstate like the plauge.
Just like the adjusters they send to people's home, they are trained to try to pay as little as possible. This is why their first offer is almost always a joke. Document everything and explain in easy to understand terms is the best approach. Also, remember not to take it personally. They will always value the house and your work less than it is really worth in order to pay less. Stand your ground on your prices and (eventually) they will realize what's going on...
Exactly what Brent said. Be sure to communicate often and precisely on the work being done and why. Document, pictures, notes, even have a scope of work made and be sure the homeowner initials next to things so they're aware of what is being done, and they approve.
Don't take it personal, the adjuster has a boss they have to answer to, make the job easier for the adjuster so they can justify the charges to their superiors.