Have not tested TuneIn, but I am sure it should be just as good as Pandora.
The biggest positive surprise for me was the JetPack "integration". It boots up and connects to the internet by the time I clear my mailbox!
Aside from losing a cup holder, I'm very happy the way this setup works, as the Echo fits like a glove in the cup holder! GM's infotainmaent system is nice, but it would hardly ever pull up a song from my iTunes library. Now I can DJ all day long without touching my phone...
P.S. it appears T-mobile doesn't charge data for any music service including Amazon Music!