iOS 9 public release note on 16th September 2015
As Apple released iOS 9 few minutes ago, Millions of Apple users around the world are trying to update their devices simultaneously. Lots of iOS 9 download requests are end up with Software update failure error because of Apple servers can’t bare that much requests. You cannot do anything about iOS 9 download error other than waiting a while until everyone calms down. You will be able to download iOS 9 over the air or using iTunes once Apple servers are ready to serve.
UPDATE – We have published a complete review of iOS 9 features and improvements. As well as news report about Jailbreak iOS 9 devices. Check it if you are much interested about Jailbreak iOS 9.