Version 2.4 also brings a "beautiful new animated login and tour experience", as well as logging in to the 500px photo community via your e-mail, Twitter, Facebook, or other social account. Finally, the app lets you edit your pictures' metadata - including title, description, tags, EXIF data, and location.
Beware, though - an user reports that the update removes the ability to explore photos or use any other functionality without logging in. We were able to confirm this, but honestly, it doesn't seem like such a big issue.
500px is free and can be downloaded from the App Store. It requires iOS version 7. The app is also available for Android 4.0 and up, and the desktop version of Windows 8. An official Windows Phone app is allegedly in the works, too.
Download (free): iOS | Android | Windows 8
500px for iOS 7 screenshots