Crash reports from app on App Store
You can get crash reports via iTunes Connect. Here's how:
- Log into iTunes Connect
- Click "Manage your Applications"
- Select your app
- Click the app icon under "Current Version"
- Click "Crash Reports" on the right side
Being only a very part-time iOS developer and having a small app that doesn't have too much going on, I've not until recently had cause to try and find crash logs. Google led me to this very old thread.
Just in case anyone else ends up on the same wild goose chase - at the time of writing (mid-2018) iTunes Connect has been rebuilt as App Store Connect and, in the web portal, all you can see is number of crashes and so-forth. To download energy usage and crash report logs from Apple servers, you actually go to XCode. Window -> Organizer -> Energy or Crashes tab [EDIT: Still correct in June 2022, XCode 13.4.1].