Apple’s done a deft job mitigating the disadvantages of true multitasking with iOS 4 by giving devs access to a few intelligently chosen APIs (like background audio) and universal state saving.
That’ll be good enough for most people and most apps without causing a huge drain on battery life or processing power, but unfortunately, the new iOS 4 APIs don’t do anything to address one of the biggest advantages to multitasking: background applications that can update or sync information when they don’t have focus. In other words, when iOS 4 comes around, apps like feed readers, Twitter clients and IM programs will still need to be open the whole time in order to suck in new information from the Internet.
Over at his personal blog, Marco Arment — developer of App Store favorite Instapaper — has posted a great suggestion to Apple on how to allow apps to update themselves in the background efficiently: give iOS the ability to prioritize periodic third-party app network requests.