Bout as good as having T-Mobile (uses their network). Will definitely vary from place to place, though. Kinda “meh” here since they mostly use band 66 for large cells which has pretty crap penetration into buildings.

My wife used Mint Mobile from 2018 until 2022 and really liked it. We moved in 2022 and unfortunately our new place had very poor T-Mobile coverage so we had to switch, otherwise we’d still be using them. She switched to US Mobile which give you a choice of using T-Mobile or Verizon.

They’re QCI 7 rather than QCI 6 though, which basically means they’re considered lower priority on the T-Mobile network. If there’s congestion (not enough network bandwidth for everyone that wants to use it), customers on QCI 6 are given priority. Every MVNO except for Google Fi is QCI 7, while Google Fi and most plans directly through T-Mobile are QCI 6.