There is still a lag time on the finger blood, it's just longer in a CGM or libre..I would calibrate on a stable BG with a couple of strips, to know how far out it was, to use this correction on the numbers you see.
I would finger test on a falling low, otherwise the ~10 minute lag time matters little. it shows up when comparing to blood levels.
Most are saying good things. You have to know,overnight, miss a meal basal checks and split bolus-squarewave with a pump to get the most out of it.
Join the libre groups on FB. It helps to look at the charts of other and get a good idea what's going right and wrong.