NEVER upgrade until at least the first patch goes out.
D-Day for iOS 7, developers issue updates, cross their fingers
I can’t speak for anyone buy myself - I updated to iOS 7 on my iPhone 4s last week. I haven’t had any crashing app issues. Indeed, even the regular crashing of the Facebook app is far more graceful now - going back to the opening newsfeed instead of just going back to the home screen.
So far, I am so pleased with the iOS 7 update that I may put off my phone upgrade a bit.