At the risk of incurring the wrath of the techies, what exactly is the reason for wanting to change channels with your phone instead of using the perfectly good remote that was provided?
I'll admit I have used the Directv app on my Droid to schedule a few DVR events that I either forgot to do, or learned about while I was away. I am just curious as to what the compelling reason is to make your phone the remote. Wouldn't it take longer to go up the wireless pipe to Directv, and back to your Receiver, rather than the few feet a direct IR/RF signal would?
If you use your DIRECTV remote/DVR in IR mode and have IR interference or slow response, it helps eliminates those issues. Since I have a Slingbox that I use with one of my DVR's, I have to keep the DVR in IR mode. That was for anyone that was going to respond with, then change them to RF mode.
Also, it eliminates the double up of key stokes that I have with my other DVR. I don't actually use it a lot, but it does help when the issues I mentioned start happening.