A huge amount. Adblocking (Safari and iAds). Information about your battery. Alternate methods to display the battery. Ability to customise the dock. Ability to change the colour of the OS to any colour you want instead of white. Ability to dim the screen and remove the blue glow from it at night. Ability to use the Messages in Facebook app. Ability to hide 70+ annoyances on the Springboard - in Notification Centre; Control Centre; Status Bar; Lock Screen; Messages/Music/Camera/Safari applications. Ability to manage the root filesystem. Ability to remove tracking from Facebook app. Ability to modify the Status bar with pertinent information (Date, Weather, etc). Ability to modify the keyboard to be MUCH better on the STOCK Apple keyboard. Ability to use gestures to dismiss applications/switch through them.
That and also hundreds of many more added uses and features that your stock ios device is not allowed to do.
But again, its not a walk in the park and its not for everyone IMO.
You have to do some leg work yourself. Research and find out what packages work, how well they do, do they have bugs or other issues, are they compatible with your device, with your ios version, do they conflict with other installed stuff, are they from a well known dev that will stick around and fix stuff or will just take your money and run instead or keep putting out crappy hacks and never update them etc....
I see people installing everything they find on cydia and after 87 hacks installed they wonder why there's glitches and what package is causing a crash or other bugs.
