One for WiFi issues, it wouldn't connect to certain networks where a friends iPhone 5 and another with and iPhone 4 sitting right next to me would be able to. Much better now on number 2.
I'm on 7 or 8. Every time it gets scratched i take it back make up some stuff and get it replaced.
About to have one because my lock button has stopped working completely.
And for those of you wondering, I did not have Apple care to receive the replacement.