Apple’s latest mobile operating system, iOS 5 is now available for download from Apple’s servers, via the latest version of iTunes.

On Twitter, Apple fans are reporting download estimates of up to four hours as the company’s servers try to handle customers trying to download iOS 5 and Mac OS X Lion upgrades, which enable users to use the iCloud suite of services. Others are reporting problems connecting to iTunes at all.

The new operating system features several new features including a new messaging service, an Android-like central notifications center, a reminder system that can set location-based alerts and — after this initial install — over-the-air updates for the operating system.

To get the download, upgrade to iTunes 10.5, connect your device to your computer and click the “Update” button on the page that appears when you plug in your iPhone, iPad or iPod Touch.

But you may want to wait a couple of hours.

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