I'm exploring the new iTunes Radio. Good selection of music and the ads are infrequent and short. If you sign up for Music Match for $25/year then no ads at all. You can pick the genre but not individual artists to play. I guess that's why they call it Radio, you listen to what's selected for you within your genre.
I've got a new program by Rogue Amoeba called Intermission that sits in the menu bar and constantly records the last 3 hours of audio. If I'm doing something else and pause it then it builds up a buffer that allows me to skip ahead when I come back to the computer and can then skip over ads. It's kinda like TiVo for your audio. I need to time the average commercial time (it's very short, like 10-15 seconds) and set the jump forward of Intermission to that amount.
Listening to Mean Old World - Allman & Clapton in the Southern Rock genre. What's not to like there?