I agree with above that the plow guy shouldn't be asked to wait for tenants to move cars. When/if our tenants complain about the plows, we always clarify that parking is included at tenants own risk/will, and snow removal is provided by not guaranteed; it's up to the tenant to keep parking spot(s) empty if he or she wants it plowed. (We had one particularly tough tenant who called, irate, because the plow had come through a few hours ago, and there were still 3 inches of snow in the driveway. It was still snowing. Right.)
I do think your other points are grounds for considering other plow companies. Do you have any small businesses in the neighborhood that use plowing? Give them a call to ask if they have a recommendation. If you get a strong nearby recommendation, it's an easy fix because you know he or she is in the area regularly. Be wary of big companies because they might be less inclined to worry about smaller accounts.
Snow removal is a pain, and I know some Maine landlords who no longer include it in the rent. We walked away from a deal partly because there was no place to safely clear snow from the driveway.