Idle quality hasn't been a problem with the MSD mags but then I don't run a race engine idle low rpm like a oem engine.
I suppose that until one tries the 12 or 20 amp versions it's hard to believe the differences versus the old mags or conventional cd ignition. I know I was surprised. I started with the old 1 and 2 amp mags many moons ago and then the MSD stuff until about 10 years ago. Now I use the 20 amp mag.
There is a quantum leap between the old vertex style and the new mags.
Starting. These days on injected engines with either style of ignition I recommend 24 volts to the starter. Makes life a whole bunch easier. Works well on giant cube engines also.
Dave Koehler
http://www.koehlerinjection.com