My Axiom was running Dartmouth (3.12) when I bought it and I’ve followed the upgrade path as it’s been issued. I can’t say I’ve found any issues with the upgrades that weren’t there before. It lacks some backwards compatibility with ST70 series instruments, the raystar125 GPS receiver and it interferes with the calibration of the dst transducer from the st70’s. You can work around all these issues but it’s not intuitive and not a function of the upgrades, it was always like it. Overall I’m happy with the latest version. Like you I don’t use the sonar feature.
Dave