The values from Libre are almost always different compared to the blood from fingertip. But using the great work from the Nightscout community one can calibrate the readings and they are very accurate.
The Libre chip stores 8 hours of measurements from every five minutes and even if the scale is wrong without the calibration the trend is right. It is absolutely useful to always see the trend and being able to react before anything bad happens. xDrip can, when correctly used, estimate how the sugar will react if I now take N units of insulin or eat M carbs.
Officially we will never get anything this nice, but if you're smart, just start building your own system. It takes time and depending where you live lots of money. But if I can understand my body better and I don't need to be afraid that I die at night, it is definitely worth it