For me, the mobile app delay is looooong...almost 45 seconds to a minute. Both on my iPhone and iPad. In fact, the iPad Raceview graphics (the one that looks like a video game) is real time, but the audio is on a long delay. So it's pretty annoying that you can't really use the two together if you're looking to make sense of it.
NASCAR.com radio feed is pretty much real time, usually even ahead of the television broadcast.
The only way I could ever recommend the app is if you're using it in a vacuum (not paired with any other visual source.) I personally love it, because it allows me to walk around the house, or go out places (like the gym, etc) and constantly be tapped into the team's radio. In that sense, the delay doesn't matter.