Having this device in college when I was doing E&M would have been an absolute game changer. The closest thing that existed was an MFJ antenna tuner for Ham Radio that only measured S11 at one frequency, and cost around $500. The next step up was to buy used equipment, which was four figures or more. Having something that goes to 1 GHz, does both S11 and S21, and only costs $50? Unreal.

Having used a modern VNA, the NanoVNA would feel cramped now... but still: E&M would have been so much easier to understand with one of these, and a few labs.