I've been going to MTEL for over seven years. It's true. These people will get you the best deal that they can. If you have trouble with your service provider, they'll go to bat for you all the time.
Getting additional accessories for your phone is just business as usual for them.
The place is usually very busy and you will likely have to wait a while for service. To their credit, they'll give you snacks and drinks while you wait, and there are plenty of places to eat and drink in the same complex.
For me it's been worth it. I have the utmost confidence that the agents are on my side, and that's not something that comes easily these days.