“Does anyone have data or anecdotal information on problems with Plasma III
EI system?” 

I have a Lightspeed on one side and a mag on the other side of my IO-550.  I think the key issues with single and dual electronic ignition systems have been well ventilated here, but I wanted to add an anecdote. 

I am completing early flight testing.  After ground runs and brake tests before first flight, touch and goes, a few hours of running very rich as part of break in, and a lot of taxi time, I finally fouled plugs after about six hours.  This was evident during the “mag” check.  Operating on Lightspeed only, there was no problem.  Operating on magneto only, I got a lot of coughing, spluttering, and missing.  I burned the plugs clean with about 2 minutes of 2000 RPM with mixture leaned way out before the engine would run smoothly again with the mag only.  It always ran smoothly with the Lightspeed only.

Conclusion: Lightspeed fires through ugly fouled plugs better than a magneto, just as advertised.  So this might be a benefit in starting if your plugs are somewhat fouled.

Better yet – don’t foul your plugs.

Your mileage may vary.

Fred Moreno