I am happy with my LibreVNA, but I also bought a better calibration kit than was provided. The quality of the kit and accuracy of the standards' characterization will directly affect the accuracy of the results. I use it in my professional practice, most recently to characterize a MIL SATCOM IF processing unit I designed for a client for a client. Jan's software support is excellent and he is making ongoing improvements.
73, Don N2VGU
Donald S Brant Jr