I have tried it and it works well. I haven't played with the latest version, but I was impressed with the earlier version. We don't use the app however, because we too have a Logitec Harmony remote that controls everything.
Even without the Harmony, I am not sure I would use the app. It takes more time to pick up the iPhone/iPad, enter a security code, and run the app, than it does to pick up a conventional remote.
Another issue is that you cannot use the app to turn the Humax on. So, you need a conventional remote around anyway. Even if you turn the Humax on by other means, it takes some time before it starts to respond to the humax remote app.