The wifey and I are big fans of IA. I saw the app for descent and thought that it might be worth a try. I was getting really sick of being the Imperial Army and having to fight the group time and time again.
For just the promise of not having an overlord/imperial force commander, I purchased it. The good news is that I really like it, definetly think it is worth it just for the app experience. My wife and I have played a bunch of games at this point. We aren't all the way through the second campaign yet. Just saw today that they are putting out another campaign soon which is an in-app purchase. Which is good, I would have felt with just the 2 (one mini, one full) that it was a bit lite.
I really hope that FFG create individual campaigns for each expansion - I would seriously start collecting them like crazy if they did.