El 4: iTunes Radio Debuts Stations Curated by Celebs and Twitter

New streaming music service iTunes Radio debuted Wednesday, when iOS 7 became available. Though users can create custom radio stations based on songs and artists, they can also discover music through featured stations.

Among the featured stations are those curated by guest DJs Katy Perry and 30 Seconds to Mars frontman Jared Leto. At launch, Twitter and Pepsi also offer stations.

The Twitter #music station on iTunes Radio will play songs trending on Twitter, while Pepsi's (co-branded Pulse #NOW) four stations will play trending and emerging pop, country, latin and electronic dance music.

iTunes Radio Devices

Apple had promised the service would use humans to curate some stations, rather than just relying on algorithms like some rival services do. Guest DJs ensure that promise is kept.

iTunes Radio is free with no ads for users of iTunes Match, which costs $24.99 for a year's subscription. It's also free with ads for non-iTunes Match subscribers. iTunes Radio will work on iOS devices (iPhone, iPad, iPod Touch and Apple TV) and iTunes on Mac and PC.

On Wednesday, Apple also revealed the brand partners whose advertisements will appear for non-paying users at launch: McDonald's, Nissan, Pepsi and Procter & Gamble.

Kindle

Amazon's Kindle app now has an all-new design, as well as a new "Collections" feature to help them organize their books, documents, and magazines. You could, for instance, have a collection for your "Favorite Kids Books" as well as "Good Road Trip Books." Content can be added to multiple different collections, so you could potentially include the same book in both.

Evernote

Evernote has a new home screen, which brings all your personal and business notes, notebook, tags, shortcuts and announcements onto the same page, new Quicknote feature, and image and PDF markup. Notes can also be shared with others through the app using iOS 7's new Airdrop feature.

Shazam

Shazam has a new look and feel inspired by iOS 7. In addition to the new look, the app now reminds you of the last thing you Shazamed when you open it. Sharing to facebook is easier and faster with the new app, and a new enhancement lets you include location, friends and comments when you share your Shazams with your friends.

Flipboard

In addition to a new look, Flipboard improved the speed of its app. The iOS 7 version of the app also includes the ability to delete unwanted comments directly in magazines, and report inappropriate users and comments. Parallax in iOS 7 also brings your magazine covers to life.

Foursquare

Foursquare updated its app's user interface, and added a new icon.

eBay

eBay's iOS 7 app adds search improvements to help you find what you're looking for, enhancements to saved searches and seller, and improved upload speed when uploading items for sale.

TED

TED's iOS 7 app sports a fresh new user interface, improved audio bar with time seeker and more.

"For this latest update, we simplified our app's interface to make its functionality more useful – a combination of efforts inspired by our own TED design ethos and Apple's vision for iOS7. As Apple puts it, "good design is design that's in service of the experience." As a result, the TED experience for iOS7 feels lighter, airier – yet familiar," says Thaniya Keereepart, the in-house product development lead for the app.

Pandora

Pandora released a new iOS 7 version of its iPhone app and a compleately redesigned iPad app Wednesday.

"We've taken all of the things that we've learned about the lean-in experience about Pandora on the web and our phone applications, and brought that the tablet with a new user experience built from the ground up around the larger screen environment of the tablet," Pandora CTO Tom Conrad told Mashable.

Optimized for larger screens, the app makes it easy to add variety to a station with artist suggestion, helps you explore more about an artist or album on screen while you listen, and provides a detailed timeline customized for each individual listener. Social sharing also comes to the iPad for the first time with the release, giving users the opportunity to publish their music activity to Facebook, or share links to their favorite stations on Twitter.

Quora

Quora's new iPhone app includes a new user interface, as well as new swiping and gestures for an improved Quora reading experience on mobile.

Night Sky 2

Night Sky 2 brings new 64bit support for the iPhone 5S, an added option for imperial units and an improved Nigh Sky Community.

Twitter

Twitter for iOS 7 got a whole new look. iOS 7 as a whole also ads a number of new Twitter features including the ability to search twitter using Siri, use Shared Links in safari to see links that have been tweeted by people you follow, and its own #music station on iTunes Radio.

Yahoo Weather

Yahoo Weather offers an new enhanced experience for iOS 7 and incorporates Yahoo's new logo.

Facebook

Facebook released an iOS 7-optimized version of its app.

The most noticeable design change is that the app's main navigation bar has been moved to the bottom of the screen, replacing the old navigation bar at the top of screen. The new design also eliminates the tool bar that slid out from the left-hand side of the app in the old version.

Photo Editor by Aviary

Photo Editor for Aviary has an all-new interface for iOS 7, and introduces a "Supply Shop" where you can find all of Aviary's Photo Filters, Frames and Sticker Packs in one place.

Image: ROBYN BECK/AFP/GettyImages