I have the HDS7 Gen3 (v3.5) + 3D Structure Scan +TM150M (+ thru-hull transducer 200Hz? in nmea2000 network) Using SanDisk SDHC 32 GB Class 10. Using Wifi nmea to stream data also to Ipad. Recording data with HDS and YachtD recorder (
www.yachtd.com/products/recorder.html)
This is my first set, so steep learning curve :-) Reading that 2D performance of 3D unit is also better than previous 2D transducers.
When scanning use, Live Structure to keep track, didn't experience any issues described by Matt. The idea is to use also Live SonarChart on the Ipad, but sonar still not recognized by Navionics Boating App.
The 3D option is a nice to have, but not using often. Expect to see more developments/updates in future....