I have used 5 sensors since November.
Have 'calibrated' each one against finger prick tests using Freestyle Neo strips in the Libre.
Sensor 1 tested consistently 0.5-6 mmol/l lower than the prick test
Sensor 2 tested consistently 0.3-5 mmol/l lower than the prick test
Sensor 3 tested consistently within 0.1-2 mmol/l of the prick test
Sensor 4 tested consistently 1-1.2 mmol/l lower than the prick test
Sensor 5 tested consistently 0.1-2 mmol/l higher than the prick test
I was happy with all of those (I know I am not on insulin, but all but sensor 4 were well within a comparable 15% +/- range expected from prick testing meters, and even no 4 was highly
consistent).
All 5 sensors were less accurate within the first 2 days and the last 2 days of use.
Am quite sure that I will hit a dodgy sensor soon, but so far I am DELIGHTED with the Libre and go into a minor period of mourning when I remove a sensor. I am limiting myself to 1 sensor every 3 weeks, to prevent total dependency.
I am wearing them, as intended, on the back of my arm, which is 'well padded', and nowadays I apply the sensor 48 hrs before activation since that seems to help with accuracy early in the sensor's life.