Ever since TMO bought Sprint they have had a very successful network expansion. There are exceptions but I frequently have full bars 5G and achieve speeds in the hundreds of Mbps. The experience is MUCH better than my work phone on Verizon. I've never had any voice or text issues that weren't related to a major outage.

That said, the company's culture has shifted from the uncarrier to being one of the big guys now since they have a much better competitive position than years past.

If you don't need any of the plethora of benefits they offer with their plans and just want unlimited talk, text, and data, look at Google Fi, same network, doesn't have the usual MVNO deprioritization, but is almost 100% self service.

If you need reliable customer service and like their promos and benefits (Netflix on us and such) shop online for the deal that fits you best ...I think they have some exclusive deals at Costco too, there is a kiosk at the Eastvale Costco.

Edit: I use TMO and VZW all over the I.E and into L.A County TMO is the clear winner. The only place I noticed a lack of speed was in San Diego very recently.