@MayaK I use the FreeStyle Libre since February 2015. Currently I am using the 21th sensor since then. Of these 21 sensors only one stopped to work after 4 days. The reader will record the errors and with these at hand you will get a replacement after reporting the problem to Abbott. For research purposes the replacement sensor comes with an hazard envelope to send the failed sensor back.
Usually the sensor has a higher error margin in the first 1/2 day of use. This can be improved by replacing the sensor 40min before going to sleep. This way you will have the first number from the device before going to bed. Then the sensor can start to adjust itself and in the morning it already has a good accuracy. At this point I check against a meter to verify this. The difference is around 10 mg/dl and mostly related to the usual time lag of cgms - which is related to measuring in the upper layers of the skin. For me the numbers of the Libre are reliable - the test stripes show a much higher variability in my opinion.
Because of my good experience so far I also dare to inject according to the Libre numbers. This is not recommended by Abbott but it works for me. My last HbA1c was 5.8% and because of the much higher rate of tests I could catch many lows when I started to drop. As a result I have less serious lows now than I had with my meter.
The comfort is excellent. Just 2 sensors of 21 did hurt a little while injecting. Just one was uncomfortable to wear for 14 days - I most likely did hit a nerve or blood vessel. The size of the sensor is the sweet spot. Big enough to stick reliably and small enough to be out of the way.
One thing is simply perfect and I can not emphasize it enough: it has no alarm function.
Why is this perfect?
For me it tremendously reduces the anxiety factor in comparison to other CGMS I have tested. I will still keep and train my senses for going low or high. At night I still have to act smart and prepare myself to prevent lows. But in contrast to the situation with the meter I can now learn from the numbers I measure constantly at night. This will give me the information I need to make small improvements.
For example I have a tendency to go low at night. To prevent this I will eat a slice of Wasa bread. With the meter it was a guessing game after waking up with higher numbers. Did I eat too much? Was it the dawn phenomenon? With the sensor I know what is going on. No false alarms just because I have been sleeping on my sensor for too long (this effect of sleeping on one side is a typical problem with other CGMS).
For longer trips with the car the handling is soo much easier than the meter. I just hold the reader to the sensor - even while driving. If necessary I drink something or eat a glucose tab if the numbers are tending to go to the low side. For me it makes no difference to take something like the Dexcom reader at hand OR wiping the Libre reader over the sensor to get the current value.
The software for the device is good - for it being the first release. I still would like to see an export of the data via XML format but that is just me. The current export via CSV is sufficient to process it in our Glucosurfer project.
The only problem with the device is the current production capacity for sensors I think. As a result you can not order more than 2 sensors at once. The next order on the Abbott page is restricted to around 10 days after the last order. Thus you might experience to run on the last sensor and to have no immediate replacement at hand if it fails. In some people this might induce anxiety and I hope they will allow to order 3 sensors at once in the future.
In general I would give it 8 out of 10 points - especially for the good price point of 60€/sensor they have currently established.