I use the Dexcom One Plus and feel it has really helped me lower my HbA1c.
It has been a real eye-opener seeing what effect different foods have on my blood sugar when it is happening, and for example, what is the best time of day to eat things - I seem to tolerate carbs a lot better later in the day, so I keep fruit and yoghurt to the evening rather than the morning, so it has less of an effect on my blood sugar.
It also has been helpful for seeing if I need to reduce portion sizes of some foods to keep the numbers down.
It definietely has helped me a lot, and although expensive I feel it has been worth it - see my signature below for the results on my HbA1c since August last year, when I started using the CGM.
I may not use it all the time later on, but at the moment I feel it is necessary for me to make sure I am on the right track.