Maintenance Ciompanies

Has anyone else dealt with maintenance companies? These are basically pencil pushers that represent other companies contracted to find and deal with maintenance needs. If so, what is your perspective on these companies? Do you deal with them and why? If so, how is your experience?

I have two I'm dealing with right now and they start off all nice and fluffy until it's time to get paid. A 45 day payout policy has turned into 65 days past due.