There are still 120 channels that do work, so I thought I'd give it a try. The app is called Sirius XM Premium Online [App Store] and it's free but requires a paid subscription if you don't already have one.
You log in (one time) with your user name and password. After a few seconds, you are authenticated and ready to explore the radio offerings.
The app allows you to browse by category, channels, or by favorites you provide. There is a shopping cart if you want to tag something for purchase at the iTunes store. (Ah, that's why Apple liked this app.)
I found the performance of the player pretty good. On a WiFi network I was able to acquire a signal or switch channels in 3 seconds. On the 3G network with moderate signal strength, it took about 7 seconds. You can get a display that tells you what is playing, or just see a list of stations.
I found the interface slow to respond at times. I often had to tap a few times to change stations. Audio quality was not ultra high fidelity, but about what you'd expect from streaming radio. I listened on Sennheiser headphones.
Howard Stern fans are very upset about not having their hero on this app. Sirius certainly could have told customers well in advance that he wouldn't be available and saved some of this pain. They handled the merger of XM with Sirius the same way. XM customers didn't know what was happening until the morning it happened. For a struggling company, it seems suicidal to constantly mislead and disappoint paying customers.
I asked Patrick Reilly, Senior VP of Communications for Sirius what happened to Stern. His response: "We aren't commenting beyond what was in the press release: Some select programming, including MLB Play-by-Play, NFL Play-by-Play, SIRIUS NASCAR Radio, and Howard Stern, will not be available on the iPhone and iPod touch. Listeners will continue to be able to access that programming through the platforms they are currently offered on."
Not a very satisfying answer. There may be very good contractual reasons why Stern and the other channels aren't offered, and Sirius XM customers deserve a better explanation. It doesn't look like one is forthcoming.
At any rate, the app works, and works well for the channels that it does have. You'll have to decide if it is worth the money versus free music apps like Pandora, Last.fm, AOL Radio and others. By the way, Dave Thomas of the Cars.com blog alerts us to their comparison of alternatives to the Sirius XM app.