I’ve been using the Elite Nero rollers on occasion over the last 8 months are so, and here’s my experience. I use them with power match and erg mode, either a P2M ngeco or 4iiii left only, depending on bike.
(1) They work better for workouts that have fairly constant resistance since it takes a while for resistance to stabilize at the target, so sweet spot type workouts are mostly fine as long as they don’t have random sprints. For an endurance workout, pettit is fine, baxter is usually a bad time.
(2) You can maintain the target in erg mode, but its not automatic like it is on a tacx neo or kickr or something, you have to work at it by getting close to the right gear and close to an appropriate cadence and then its fine. It’s in between something like a neo and a dumb trainer.
(3) I don’t really calibrate the nero that often since I’m getting power from the PM, but it can help if you start to regularly get into this strange sine wave like loop where it can seem to stabilize at the target no matter what I do in terms of gearing and cadence. In that situation, calibration helps.