Though Thursday's release of the iPhone 4 is getting the most fervent attention, Apple's iOS 4 is just as significant. CNET takes a look at the biggest offerings in this initial review.

Retina upgrade. The newly released iPhone 4 further ups the gaming ante with its visual enhancements—specifically the 960-by-640-pixel Retina display at the heart of the phone’s new form factor.

Now, IOS 4 makes the iPhone capable of running multiple applications simultaneously. Folders: Users can now better organize their iPhone apps with home-screen folders to cut down on clutter.