This spring, given the cost of electricity, I'm going to ensure I get top performance, by insisting that a technician charge my system via superheat calculation. I know that this is the most accurate method, but also takes a bit of special equipment, and some time.
I fear that if I ask this, I'll get rolling of the eyes from those that don't love their jobs, shall we say. I know that talking about pricing is forbidden, but I've seen other solicit feedback & find companies to do work in these forums. If I'm out of line, let me know; otherwise, if you're in the Baltimore / Howard County, Maryland area, and would like to charge my system via the superheat method (straight A/C, no heat, no heatpump), then send me an instant message on the site here. I have a 2006 2.5 Ton American Standard 13SEER system.