I've never paid by the minute. Tesla Superchargers often deliver less energy per minute when they're busy (sometimes much less!) and it would be frustrating if they charged per-minute.

Other systems I've seen (Chargepoint) also seem to be energy-based.

The Supercharger network is well done. It's a shame that they took this long to open up to other car models because they really do get a lot of things right.