Marco Arment has released another update to his popular Instapaper offline reader application introducing synchronization of reading positions in articles between multiple iOS devices. The new feature allows users of more than one iOS device, such as an iPhone and iPad, to switch back and forth between devices and easily pick up where they left off on the other device. The update also adds the promised background task completion for iOS 4 devices allowing synchronization with the Instapaper service to complete even after you exit the app. Other enhancements in Instapaper 2.2.5 include dramatically improved performance and accuracy when rotating the device between portrait and landscape mode, the ability to e-mail the full text of stored articles and improvements to tilt-scrolling and password entry on iOS 4. Instapaper is available from the App Store for $5 and is a free update for current users.