The Napster name was eventually bought for a legal streaming service similar to Spotify. When Spotify launched in the U.S. Napster threw in the towel and merged with Rhapsody. Now, after 10 or so years, Rhapsody has about 1 million subscribers, about 40% of which came from the Napster merger. Spotify after about 3 years has 2.5 million subscribers.
If you really can't stand the ads (and who wants a condom ad between movements of a Beethoven symphony?) you can pay $5 a month for computer streaming only, and for $10 a month you can also have it on multiple mobile devices and save tracks for offline listening. I'm now a premium subscriber and I have tracks saved on my Kindle Fire and iPod Touch.