I have cricket, which uses ATT towers (I think it might even be owned by ATT). No problem with text or calls, but internet seems a tad slow, but could be because I bought an older phone. The internet seems ok on wifi.
I don't use much internet on my phone, so I have the cheapest offering they have, and it costs $30 month.
Not real sure I will ever have service directly from ATT, Verizon or T-Mobile again, and don't really understand why they sell their service so cheaply to other providers.