I think the iTrains are a little cheaper per workout (
www.iTrain.com) and you can do a monthly service where you download 6 workouts for $9.99 so that way you have different options every month - they come out with them monthly, too.
Cardio Coaches are great, too. I have both. The Cardio Coaches are interval training. You climb a hill for x number of minutes, then you have a 2 minute recovery.
The iTrains are more random. They are usually 6 minutes on with 1 minute recovery for the length of the workout, but they all vary.
Both are excellent programs.
You can also check out the podcast on iTunes - they have many free podcasts for runners.
Oh, and both are very easy to install. Simply click "save" and save to your iTunes music folder (under my documents, then my music). It will then download to your computer, and you'll see it in iTunes.