The 2.0 app was faster, usually instantaneous in fact. The only time there was a delay was when it needed to update after a settings change (refresh navigators, etc). But in normal use it launched nearly instantly. I assume others have the same recollection and experience? If not, perhaps I was just lucky. I do not know.
The 3.0 app is a lot better than it used to be, for sure. But still takes 1-3 seconds, and often can be longer. The first time I launched it today it took over 10 seconds. I suspect when it takes a really long time it's due to something being paged out of RAM on the controller, or any of a million other possibilities (since I don't know for sure what's happening during that app startup). Thankfully those kinds of delays are not the norm. But the end result for me has been I've lost faith that the app will be available when I need it the same way a remote or button is. Others of course may not care. But I'm not happy with it and I really hope we eventually get back to the way it was with 2.x.
Incidentally, based on your comments I tried Lutron, the iOS Home App and C4 and C4 is the slowest each time. Lutron and Home start under a second (Home is basically instant), but C4 takes 1-3 seconds. As before, this is somewhat subjective as many factors can contribute to slowness, but I can at least attest to C4 being the slowest of these in my case. Things get worse when you look at real world scenario. I can open up the Home app or Lutron and turn one of my lights on and off way faster than I can using the C4 app. By way faster it might be 2 or 3 seconds faster, which doesn't seem like a lot. But it feels like forever and makes me not want to even bother half the time.
John