I don’t know anything about Tamdem, but I have been using a 670G for 3 1/2 months. I have heard that the Guardian sensors can be great, but my body’s chemistry seems to interfere with it. I have about 4 good days, and then it gets less and less accurate until it fails on the 5th or 6th day. I have had only one sensor last 7 days, and that one was still increasingly inaccurate after the forth day. I am not alone with this problem, but Medtronic is still trying to figure out what the cause is (chemistry, immune system, … ???). They are very good about replacing failed sansors. They have been great about this. Their Tech Support people have been unfailingly available and helpful.
I had a Dexcom for several months before getting a pump, and I never had these problems with it, so I guess that these sensors use different materials. That being said, I LOVE my pump. Medtronic makes a great pump, and they’ll have to pry it out of my cold dead hand.
My doctor & CDE & Medtronic have not figured out yet what to do about this problem. As a last try, Medtronic replaced the transmitter under warranty, in case the problem is that, but the problem still occurs. Maybe they will figure out some compromise after I have been using the new transmitter for a little longer (I’ve had it for 3 weeks).
As for Auto Mode, I don’t use it. It bases it’s behavior on the previous week or so of your body’s BG patterns, and your behavior patterns (work, sleep, exercise). I am going through perimenopause, and my erratic hormones mean that I don’t really have a predictable “normal” for it to go by. I have created several basal patterns to deal with varying levels of insulin resistance, and use Temp Basals to deal with exercise and sudden hormone-induced rises and falls of BGs cause by peaks and dips of insulin resistance. This is very easy to do with this pump, but this is my first pump, so I don’t have a basis for comparison. It is worlds better that the Humulin N & R thay I used for the first 30+ years of being diabetic. (Yes, strait from Humulin to a pump! Yipee!!!)
I hope that this helps. I don’t know if you can get a 670G trial period to find out if you are one of the unlucky few, but during the first 4 days or so, the Guardian sensor is pretty good. So, it might work out okay for you.