About 3-4 years ago I tried the MM system, then called the Soft Sensors. In the one month time that I tried them (during the refundable period) they were nothing more than random-number generators. I forgot how many sensors I tried, but it was lot and I spent many hours with tech support. I ended up getting a refund. That very same system worked great for my wife. go figure.
Fast forward to Sept 2014. My wife switched from Soft Sensors to MM Enlite. It worked even better for her, so at her insistence I tried one of hers, along with her new 530G pump. Shockingly, it worked superbly. I was eligible for a new pump in early December, so I opted to also get the Enlite with it. Things went downhill. I have had 5 sensors replaced due mostly to failure of the sensors to output a high enough signal (called "ISIG"). I had so much trouble with several sensors in a row that I called MM to start the refund process. After a day without a sensor, I felt "naked" and so I installed a new sensor. It worked reasonably well, so here I am, 2 months later and I've had some sensors that have worked well way past the expected 6 days. I had one work great for nearly a full 14 days. For me, the key seems to be nothing more than finding the right area on my body to put them.
I'm not writing this to suggest anyone use a particular brand of CGMS--I'm just saying that by persevering, I'm now getting the good results much of the time, that I never thought possible. If you, like me, feel "naked" without a sensor perhaps working closely with tech support can get you some better results. One thing MM has said is that lean people have a hard time wearing the sensors as they must go into a layer of fat. The only appreciable fat i have is around my belly, so if I run out of viable spots there, I'm out of luck. Good luck to you!!