It puts a lot of the iPhone settings on one screen, with a toggle on/off switch. You can access it from any screen, much like the new Notification Center, and can customize which settings you want.
Things like Airplane Mode, Bluetooth, Wi-Fi, Brightness, activating the LED light, etc can be EASILY accessed without having to dive into the different pages under Settings.
----------
Icon Project is not an app. It's a Safari shortcut. It's not good enough as it does not offer the speed and convenience that SBSettings offer.
It puts a shortcut on any screen, not just the home screen. So they take up space, or you can put them all in a folder, which adds another step. To get to Icon Project, you have to get to that page, open up the folder (if used), then click on the settings. That then opens up a Safari page, which then automatically takes you the appropriate Settings page. From there you still have to toggle on/off.
SBSettings is a simple two-step move. Swipe to open the menu, tap to toggle. Icon Project is much more involved.