I never had Sirius in the past, and can't say I really plan on using it. I pretty much have the two local stations I listen to, and if I'm traveling out of state - IHeartRadio app lets me still listen to them. Otherwise, it music on my IPhone. Since my commute is pretty short I don't listen to the radio often.
I agree about the UI, not the fanciest. But I think if they released a SDK for it - people would create some cooler ones.