Apple offers their latest operating system, OS X Mountain Lion, for a reasonable rate in your local currency. However not all existing Mac's meet the minimum hardware specification, and are therefore limited to it's predecessor Mac OS X Lion. This is typical of new operating systems as the demands on the system hardware tend to increase or sometimes older processors architectures are no longer supported for upgrade, such as Apples transition from PowerPC to Intel processors about 5 years ago.
This blogpost is about the specific implications of running Mac OS X Lion along side the latest versions of iLife and iWorks applications supporting iCloud.
Firstly Shared Photo Streams are NOT included in the latest versions of iPhoto and Aperture when running on Mac OS X Lion. This can not be due to a hardware restriction as the personal Photo Stream (up to 1000 most recent photos) works perfectly and keeps all your latest snaps up to date just as on iPhones, iPads and Apple TV's. So why omit it? To encourage you to upgrade to a new Mac?
When it comes to iCloud storage of documents for iWork the Apple webpage says: "iCloud requires iOS 5 on iPhone 3GS or later, iPod touch (3rd and 4th generation), or iPad; a Mac computer with OS X Lion or later". So you would assume that Pages, Numbers and Keynote would be fully integrated with iCloud document storage as shown on the Apple webpage advertising each service, assuming your Mac is running either Lion or Mountain Lion.
This, however, is not the case. From the Help file in Pages: "Updating documents using iCloud works differently, depending on whether you’re using OS X Lion or OS X Mountain Lion (v10.8)". How different you ask? Well the method of transferring files on Mac OS X Lion is to use www.icloud.com! Cloud services such as Google Drive and Dropbox, for just two of many examples, which include a desktop app, syncing automatically, offer a far neater solution to push your content to cloud storage than via a web browser. The web browser method is a handy tool for when you are away from your computer, not a primary workflow. The requirement is then that you manage the library on your Mac and choose what to upload or download. iCloud is supposed to 'just work' and the versions feature should stop you losing old parts of a document.
These two examples could be included on older systems if not for Apples need to add new features which are unique to the latest OS. In many cases systems which can't run Mountain Lion can in fact run either Windows 7 or Windows 8 using boot camp and can enjoy Shared Photo Streams with the iCloud application for windows.
So in summary, always remain up-to-date or unfortunately expect some disappointment.