Just figured out something.. when its the first time downloading the app it is possible to use the "Is downloading update" but the "On update ready" won't be fired (because the event that is fired is Cached event). But if it was cached the first time then next time you get an update the "On update ready" is fired. I had to handle both case which resulted in using some kind of indicator mixed with loadingprogress = 1 instead of actually using "On update ready" because i couldn't handle both scenario with this same code.
That would be nice to be able to handle the cached event too. Was just a suggestion! :)
<img src="http://s10.postimg.org/rbqceslix/c2_cached_event.png" border="0" />