How is Xfinity's mobile coverage?

I am thinking about moving from T-Mobile to Xfinity. But, I am wondering from anyone how their coverage is and if you are happy with the service. I got a email for a free phone and no credit check. I guess because I have been with Xfinity 43 years? Anyway, I'm not worried about the credit check but a free phone peaked my interest being I have a Samsung Galaxy S8!!! Yikes, I know. 

I would sure appreciate any feedback good or bad from anyone who has actually had or do have their mobile service with Xfinity.

Does anyone also know what towers they use?

Thanks everyone!