Apple's Lion operating system was originally launched in June as Mac OS X Lion v10.7.1, but has been upgraded this month to version 10.7.2, adding many new features, and also updating the OS with a host of security improvements.
This is the eighth iteration of Mac OS X. The OS release before Lion was Snow Leopard (v10.6) [see picture].

Apple says the upgrade includes 250 new features, with one of the biggest ones being access to the company’s recently launched cloud storage system, iCloud.
iOS and Mac OS X share a common code base (C++) so it’s easy for Apple to lift features from iOS and drop them into Mac OS X. In Lion there is a spillover of features from iOS, such as better multi-touch trackpad gesturing.
We reviewed Lion on the 11in model of the new MacBook Air, which has second-generation Intel Core i7 processors and Apple’s implementation of Intel’s Light Peak technology, Thunderbolt.

Lion also has built-in support for Thunderbolt hardware and does not need the firmware updates that Snow Leopard required to work properly.
Install
The version of Lion installed on the MacBook Air when we received it was 10.7.1. We checked for software updates, and apart from an iTunes update from v10.4 to v10.5, there were two updates to Lion [see picture].

The most important update is the 785MB Mac OS X update, an actual point release of Lion just three months after its initial launch.
The major reason for this update is to enable Apple’s iCloud, which allows Lion and iOS 5 users to use the cloud to store content and synchronise it across multiple devices.
The second update is a 452MB fix to Lion’s Recovery [OS re-installation] feature, addressing an issue with Find My Mac when using a firmware password.
In use
So how does Lion compare with Snow Leopard? Well, running them side-by-side you’d be hard pushed to notice specific user interface differences, but there are significant differences in the feature sets, and a large number of security fixes.
The only problems we had with Lion was using the new overlay scroll bars, and in some of the new multi-touch trackpad gesturing.
The new overlay scroll bars are thinner than before, and also only appear when the cursor moves onto pages that require scroll bars. After a time the scroll bars disappear and it can be hard to get them to reappear and grab them.
The rest of the new features, such as iCloud access, Launchpad, Mission Control and the ability of applications to use the full screen performed well.