My favorite feature on my Denon is it's HDMI Monitor Out 2, and that I can control everything from my ipod.
For example, I have a small Samsung LED LCD in my room hooked up to the 2nd HDMI out, so when I go to my room, I just pull out the ipad/ipod and flip HDMI audio out to Television, and the Monitor Out to 2 and I can then watch blurays from my PS3 or stuff on my Apple TV. Fantastic. I couldn't do without that.
The app, by the way, isn't the Denon Remote, but another - better one, called DeRemote.