Is tmobile good w/ the iPhone 5s?

So i'm thinking of getting a family plan with tmobile (2 iPhone 5s and a basic phone ) and i was wondering if tmobile is any good? I'm getting the 500 mb of data and apparently the internet slows down after you use that much? But if i'm on Wi-Fi it doesn't matter does it? The plan is the cheapest i have found. Its like $145 so how is tmobile?

I have been a T-Mobile customer for over a decade. I'm a happy customer. There have been issues now and then but there will be with any company/service. However, they issues I have had have always been addressed to my satisfaction.

Our account includes four voice lines and a mobile broadband line. I use an iPhone 5, my two teens each just got the iPhone 5c and my husband uses a basic phone. Our costs for the voice lines is $100 a month. The mobile broadband is $10 a month and I do pay for extra data on my line.

The 500 mb is part of the plan. You can continue to use data after that, but it is slowed down (unless you purchase more). You can still use Facebook, check email, use the internet, play games… But downloading music, streaming videos, etc.becomes nearly impossible.

Using Wi-Fi conserves your cellular data, so if you have a Wi-Fi connection at home, school, work, out shopping use that instead when you can, especially for heavy data usage.

My children have had their phones for approximately two weeks. Even without downloading music, videos, etc. They have both already exceeded the 500 mb. Granted, the phones were new so they downloaded a lot of apps.