As expected, Steve Jobs took to the stage Monday at the Apple Worldwide Developer Conference in San Fransico to reveal iCloud, a collection of cloud services designed to work seamlessly with its iOS and MacOS X devices and computers.

Jobs explained that moving from a PC centric to a cloud centric model was necessary in order to simplify getting content onto multiple devices. “Keeping those devices in sync is driving us crazy,” admitted Jobs.

The free iCloud service will ensure that content from all Apple devices, such as photos taken on an iPhone, will be automatically uploaded to the cloud and then pushed back down to other Apple devices such as an iPad, without any need for user interaction.

The former MobileMe services – Contacts, Calendar and Mail have been re-architected to work with iCloud, while all App Store and iBook store purchases will be distributed to all devices, up to a maximum of ten, not just the one the purchase was made on.

iCloud will also now sync changes made to any documents created using Apple’s Pages, Numbers and Keynote office apps, and push them out to other devices. Up to 5GBs of storage is offered for free with additional storage available to buy. Meanwhile, the Photo Stream service will push pictures taken on an iPhone to other devices, storing photos in the cloud for 30 days.

iTunes in the Cloud will for the first time allow previously purchased iTunes music to be downloaded to all devices at no extra cost, as well as new music. A brand new paid for service called iTunes Match will scan all music in your iTunes library and replace it with a 256kbps AAC DRM-free version, which will then be available to stream in a matter of minutes. This is a major advantage over Amazon and Google’s cloud music plays, which require all previously acquired content to be manually uploaded before it can be streamed back to the device, which for large libraries could take weeks. Apple will be charging $24.99 for the privilege however, and as with Amazon and Google’s service it will only be available in the US at this stage.

The iCloud beta is available immediately to developers and will go public with the release of iOS5 and Mac OS X Lion later this year.

While Apple’s iCloud service is impressive, it is not the first to market with many of these features, with Google and Amazon already launching their cloud plays. However, Giles Cottle, Senior Analyst at Informa Telecoms & Media does not believe that the delay has hurt Apple.

“It’s the fact that iCloud brings all of these features together in a compelling, easy-to-use and intuitive manner – rather than the features themselves – that makes the iCloud proposition. The basic user proposition of cloud services – being able to access your photos, documents, video and music everywhere – is fairly straightforward. But it was always going to take someone like Apple to really educate mass market consumers about the value of cloud-baesd services. We are, it appears, on the cusp of that moment.

“Most crucially, Apple’s tight control of its device ecosystem means that iCloud is much more likely to, as Steve Jobs puts it, “just work”. Apple’s total control of the device and content ecosystem has been heavily criticised in the past, but, if iCloud works as well in practice as it did in today’s demo, it’s a stunning validation of the power of closed ecosystems.”

Apple also announced details of iOS5, which now includes an enhanced notification system that stops system messages interrupting your activities (Apple has reportedly hired the iOS hacker behind the popular MobileNotifier app for jailbroken iPhone devices – Peter Hajas), and closer system integration with Twitter. iMessage will also bring free messaging between all iOS5 devices, mimicking Blackberry Messenger, while iOS5 will also allow first-time set-up and software updates without requiring a connection to a PC.

Finally, Apple said that Mac OS X Lion, offering 250 new features, would be available as an upgrade in July for $25 or £20.99.