I carry a tiny multimeter that cost just a few £££ on eBay. It's all you need to diagnose the sensors or any other aspect of the electrical system.
Diagnosing the Ecu is simple (if it doesn't do anything instead of its startup test then it's foobarred and needs replacing. Which is uber rare these days).
I can understand those who dealt with points and a carb finding the efi system bewildering, but it's just a question of learning how it works just as you had to learn how points and carbs work. A lot of ppl seem reluctant to learn and just write it off.
I also appreciate early electronics were not especially reliable, so ppl has a broken down bike in the mid 80s and no idea how to fix it. But it's 2012 and electronics have moved on.
They switched to efi primarily for emissions followed by reliability.
Best bike to have is the one you can fix, be it carb or efi.