Repository overview is perfect for mobile phones and for what iOctocat is built for, easy access on the go for repos. It displays the description, a quick way to open detailed info and a quick way for bookmarking for later.
iOctocat is at feature parity with github.com when it comes to managing issues. You can view & open all open/closed issues, search issues, filter issues, open new issues, edit old issues including all the meta data and comment on issues.
For some features, users need to buy the basic or pro version of iOctocat which come as in-app purchases. Private repositories and notifications require the Basic update. Receiving push notifications and support for GitHub enterprise require the Pro upgrade.
CodeHub is almost at feature parity with Github.com itself as it supports the most major and widely used feature of GitHub. It has full support for issues, pull requests, notifications and repository management.