In late February 2020, in preparation for a planned trip to Alaska in June 2020 (now likely delayed/deferred), I decided to go ahead with my planned Magneto Inspection & SureFly (SIM4N) installation. Note that I used the improved power lead/fuse holder from SureFly after issues were identified early on with it (like the one's Rich mentioned in this thread) and my mechanic also put a boot over the hot terminal as Rich also suggested.
Based on everything I read here and discussion with my A&P, I decided it would be best to retain the Slick Start system, so I replaced the Right Magneto with the SureFly. I was at a total of 543 trouble-free hrs since my last rebuild by QAA in Tulsa, OK in April 2018 (Savvy recommends IRAN between 500-600 hrs), so I had QAA in Tulsa do the 500 hr Inspection (IRAN) on my Left Mag. There really were no issues with replacing the Right Mag, since it was easy to move the RPM sensor to the Left Mag as already discussed in this thread and the connection to Cyl #3 intake manifold (to take advantage of the timing advance at altitude) was also close by (note that I found the correct size 90 deg fitting at a nearby Ace Hardware).
My plane (N905PA - bought from Antoine in 2017) is an '08 XLS with PowerFlow exhaust, so at 12 yrs old I also decided to replace the spark plug wiring harness, however I retained my Tempest Fine Wire spark plugs (cleaned).
Due to the Pandemic, I have only been able to put ~14 hrs on the SureFly to date, with no long cross-countries, so I have only limited observations:
1. Starting - has always been easy, so no real difference observed.
2. My first 8 hrs on the SureFly were all at <5000' and were trouble-free. After seeing Rich's note re intermittent "stumbles" at higher altitudes, I decided to climb to 7000' on a recent flight. As I approached 7000' my engine also stumbled but for ~20 sec (EGT's were erratic, up and then down), then returned to normal with no other issues. We subsequently checked all the SureFly connections, as well as, the conventional magneto and did not find any issues. I have not observed the brief intermittent "stumble" issues highlighted by Rich and with an additional 4 hrs (including a climb to 9000') since we checked everything, I have had no issues. At this point, we have no idea what caused my engine to stumble that one time.
3. Power/Speed/Smoothness - no discernible difference yet.
4. Fuel consumption - need more data, but perhaps 0.2-0.3 GPH savings.
5. CHT's - are definitely higher, by ~10F and appear less sensitive to fuel flow / power settings than before (I need to look back and find more comparative data to better assess the impact).
6. LOP operation - I am now able to operate LOP ~25-65F with a smooth engine (versus only 5-30F previously). I completed the Savvy Test Profile at 9000', which if you are familiar with that, ends with a test of your magneto/wiring harness by running on 1 Mag at a time while operating LOP at the onset of noticeable engine vibration. In my case, this was with the last cylinder to peak at ~25F LOP (other cylinders were ~40-65F LOP). I observed the usual increase in EGT's (~125-150F) when switching to the Left (conventional magneto), but observed a smaller increase (<100F) in EGT's when running only on the SureFly (is this a side effect of the timing advance on the SureFly?). Note that prior to this Mag IRAN/SureFly installation I could never operate more than 5-10F LOP on the last cylinder to peak without excessive roughness, so this is a definite improvement.
I'll share any additional learning when able.