There are only two companies in the United States selling continuous glucose monitoring systems, Dexcom and Minimed (the diabetes division of medtronic).
I have purchased CGMs from both companies before my insurance would cover it for me (100% out of pocket), and since I got insurance coverage, I have used insurance to use both companies (in case y'all are wondering, I used minimed's sof sensor guardian system, then Dexcom 7+, then Dexcom G4, and I'm now on minimed's 530G with enlites).
My experience is that they have both dropped the ball on multiple occasions. I have had extremely frustrating experiences with both companies. It really tends to depend on who you get with the company.
I strongly suggest that YOU be the one to keep pushing and be pushy pushy pushy. I also suggest you choose based on the systems (or possibly the cost) and not on the customer service. Minimed HAS more customer service- they don't make such a dummy proof device- but they are very capable of telling you that something will cost one thing and charging you another, or double billing you (at one point they "lost" my check, I sent them another, and they cashed both), or telling you that you have insurance coverage when you don't (that's happened to me twice with them). And they also have the problem that, say, one person asks me for paperwork, I fill it out, and two months later when I'm trying to order supplies they tell me they can't because that paperwork hasn't been filed yet.
Dexcom, OTOH, was really bad about contacting my doctor for me- they'd say they had when they hadn't. I really needed to do that for them. And once I did get insurance coverage, it was maddening to note that my "special cash price" that I'd paid below the list price for buying it with my own cash and no insurance, was higher than the insurance price.
Anyways, if you like medtronic better, good for you, but don't go thinking they're all that great either. Focus on the product, not the company.