I completed the D-180 update today and it went exactly as Marty's went in post #20 above.
To that, I can add:
I use the RETN FLOW parameter on the Fuel Flow menu as well as the K-Value and I had to reset that, in addition to the K-Value.
The Magnetic Intensity and Magnetic Inclination were reset to "blank", and I had to put in my saved settings, but I don't know if the compass has to be re-swung. I did note that the compass heading reading was the same as before the update.
My AOA display did not reappear after the update. I have not checked the clutter menu for that items status but I may have to re-calibrate the AOA.
If you have the AP-74 autopilot it will reappear with all lights lit after the update and if you do a "Detect Firmware Version" on the Product Support Program screen you will see the AP-74 and servos are not found. That is because doing a firmware upgrade you are starting over with the DSAB network and you need to do the DSAB configuration per the installation manual and follow that with the servo calibration and servo test just as you did on the initial startup of the autopilot. Once those things are done, then you can re-install any custom settings you had on the servos and everything should be working. If you "Detect Firmware Version" again you should now see the AP-74 and the servos listed:
I also have the D-100 and that unit is updated separately from the D-180:
That went smoothly and I don't have many custom settings on the D-100 but did find that all my screen rotations were wiped out and as I could not see EMS data from the D-180, I thought there was a communication problem. As it turned out I just needed to reset the screen rotations as the EMS screen was no longer in the screen rotation.
This update has some some important fixes, the main being correction of the NAVSRC lost which resulted in the autopilot dropping off the GPS magenta line and going to TRC mode. On my ship this would happen probably 5 times in a 200 mile run.
Also my altitude hold would always offset about 20 feet higher than set point. If I set ALT to 6500, the autopilot would hold it at 6520. This upgrade is supposed to improve the target hold.
There is also supposed to be improved autopilot tolerance of EFIS installations that had higher than ideal vibration levels. I don't think my autopilot had this as an issue, but don't know, it could have.
There is also improvement to fluctuations in at least one type of sensor. I hope so, a lot of the sensor needles fluctuate more than I like.
It took me about 2 1/2 hours to do back-ups, install the update on the D-180 and D-100 and go through all of the resetting of parameters.
I hope to fly in the next few days and check how things are working. I don't anticipate any big issues, but there will probably be some tweaks necessary.