You can add it and drop it as you wish, but keep a couple things in mind:
The thing doesn't go into landscape mode so if you have a car dock like I do, it is a pain.
The app will cut out for no reason, even with a full 3G signal.
The app tends to sound like an AM radio sometimes, and the quality of a song will go up and down during the song, which can be jarring. It sounds like someone hit the needle of a record that's playing when it happens. Quite annoying
The lineup for some strange reason is very limited on the app. You don't get the whole XM lineup. I was really shocked to learn that all of the sports channels are gone, well at least the play by play channels are, so no NHL playoffs and no MLB on XM.
I have used the app for about 6 months, but I am going back to the satellite radio unit.
The last thing that pisses me off about this app is it randomly restarts when you exit the app.
To me, it just doesn't cut it.