I have to agree that iTunes Radio - compared to Pandora and Songza - is by far inferior.
The recommendations are good, but it lacks variety. Even though I selected exactly this. I always here the same bands, the same songs. When I listened to a station for, let's say, four or five hours ( doing a project etc. ), I probably a few songs twice and only 6 or 7 different bands. Also, sometimes it just stopped working and I had to either restart the the phone or wait for a few minutes.
The best service by far is Songza, though. After I tried iTunes Radio, I used Pandora which was, at that time, really eye-opening. But then, I discovered Songza.
New bands, new genres, new everything. No repetitions, professionally crafted playlists according to specific moods and activities. I LOVE IT! It's my constant companion along with Spotify on the road.