One tricky thing about the space -- you have to know when it's appropriate (and not) to compare services. You can make associations on one variable, but not another. I do my best to insert the proper qualifications and nuance in my analysis.
Apple's iTunes Radio
Bottom Line: It's underwhelming. If you have never used an Internet radio platform and have no plans to do so, iTunes Radio could work. Your grandparents -- even if they're no longer alive -- are, ironically, best suited for iTunes radio. But they probably don't own Apple products so it's a wash.
What's It Good For: Mindless listening. Making purchases to your existing music collection (though there's really no need to; see Rdio section). Drooling over Canadian hotties such as Sarah McLachlan because the artwork Apple uses in iTunes Radio appears more vivid than any other Internet radio platform I regularly use.
Why You Might Think It Sucks: Because, pursuant to what's it good for, iTunes Radio provides a largely mindless listening experience. But not mindless in a good way.
I cue up Sarah McLachlin from my collection. I ask iTunes Radio to create a Sarah McLachlin station. And, nine-point-nine times out of 10, it follows up with something like Alanis Morrissette's Ironic. A basic genre-based play. And it keeps doing that over and over again the entire time you listen. Until you just can't take it anymore.
When you enter iTunes Radio, often via your iTunes collection, Apple serves you a glorified Genius playlist. That's not good enough. Not in a space where others have come to play. For real. As people who eat, sleep and drink music.
If you have a limited collection of music, narrow tastes and don't like surprises, iTunes Radio could be enough for you. Though I still think you'd be better off elsewhere, even if you're not a big music fan.
But that doesn't matter because, as I explain in this article and at the links contained within it, Apple didn't come up with iTunes Radio to be a player in Internet Radio.
Platform Observations: I don't use Apple TV. And I note no meaningful differences between iTunes Radio on my Macbook, iPad or iPhone.
Additional Thoughts: Despite Apple cutting corners on iTunes Radio, I still love the iPad Air my wife bought for me and I can't wait to upgrade my iPhone later next year. In other words, iTunes Radio might only marginally help Apple, but it certainly will not hurt it.