What is everyone's favorite pick for coil cleaners?

Concentrate? Foamy no rinse? Evaporator specific? Condenser specific?


I purchased some of the green concentrated Kleen Coil from United when I did an evaporator cleaning (evap completely blocked with a blanket of drywall dust).
I recently had a call where the condenser was a little dirty, but I was hesitant to use it on the outdoor coil - as it does say 'evaporator' on the bottle. How critical is that? Could I have used my Kleen Coil mixed 3:1 water:concentrate or do I need to make sure I get other stuff for the outdoor units?

How critical IS this stuff? It's not outrageously expensive, and it sure seems to work, so, do you even use it yourselves, or need it?