Sometimes Apple is first to bring a feature to market, and other times, Steve Jobs says, Apple is the "first to do it right." is the latest example of Apple waiting to implement a feature until it could overcome one of the greatest challenges, in this case battery life. A single application--a streaming Internet music player, a GPS location tracker, or a simple newsreader--can take a decent bite out of your iPhone's battery. Multitasking in iOS 4 will allow more than one application to take a swipe at your battery at the same time--you can upload multiple photos to Flickr while streaming music with Pandora over 3G and downloading articles in Instapaper. Apple wanted to wait until it could fortify iOS to properly manage the balance between data-gobbling smartphone applications and getting your iPhone through the day.

Multitasking in iOS 4 isn't quite like multitasking on your Mac, where any application is essentially free to do whatever it wants in the background. Instead, iOS 4 allows applications to perform some key tasks in the background, like playing audio, checking your GPS location, or uploading pictures. But save for a handful of tasks in very specific cases like the ones we just mentioned, most apps will actually use another iOS 4 feature called "Fast App Switching" to simulate the effect of multitasking.

Fast App Switching allows an app to save exactly what you were doing when you switch to another app. For example: Say you start jotting down some ideas in Evernote, then switch to Settings to turn down your display's brightness, then answer a phone call before you get to your preferred brightness. Settings and Evernote don't really need to continue running in the background during that phone call because they're not doing anything. But when you switch back to them, they should return you to the exact screen, or the exact character in a sentence, where you left off. As long as an app is optimized for iOS 4's multitasking and Fast App Switching features, it will finally provide this convenience.