Don't Install It If You're Leery of iOS 9 Problems
If you aren't dealing with any major iOS 9.0 problems, you might want to hold off on iOS 9.0.1. At least for right now.
We've started to see iOS 9.0.1 problems emerge after the update's release. These include issues with battery life, connectivity and even security. Downloading iOS 9.0.1 puts your device at risk. There's no real way to predict what you might see, even if you do prepare your phone or tablet.
The only thing you can really do is wait a few days for the dust to settle to see what people are saying about performance. If the overwhelming majority of users claim that performance is good, then you have more reason to install the iOS 9.0.1 update.
Your answers might not come for a few days or even a few weeks so hold off until you're feeling supremely confident.