By Darren Waters Technology editor, BBC News website

Leopard was in development for two and a half years

A new operating system is often more about anticipation than delivery. There are so many new features that a typical user will never think about, let alone use.

The key question is: Will it change the way I use my computer for the better? And the answer for Leopard is a qualified yes.

Installation was painless - an hour to upgrade from Tiger with just a few questions to answer and I was ready to go.

Leopard's features

At first glance little seems different - icons on the desktop have an unfamiliar shape, the menu bar at the top of the screen is translucent and the dock has a pseudo 3D aspect.

My Mac - a 2Ghz Macbook with 2GB of RAM - should more than cope with the upgrade but a few clicks in and my machine went into a Kernel Panic and a pop-up window told me to switch off and restart.

Thankfully, since then the machine has run smoothly and many applications seem snappier and more responsive.

The only area that is noticeably more sluggish than under Tiger is my Mac's ability to re-connect to my wi-fi network when I open up the lid of my laptop, or wake it from sleep.

It used to connect within a second or two but now takes between five and 10 seconds. It is not a major problem but an irritant nonetheless.

Despite the boast of hundreds of changes, it is only a handful that will impact on most users and they are a mixed bag.

Time Machine is the killer application - it makes backing-up your Mac painless and turns a chore that few of us remember to do into a pleasure.

If you've lost a file or made a revision to a file in the past, you can simply roll back the individual document to before the changes were made. Ingenious.

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Time Machine works for files, folders, applications and the entire system - and it is handled through a fool-proof interface.

Be warned, however: You need a decent sized external hard drive to make it useful and the initial back-up of your system can take many, many hours.

The most useful new feature in Leopard is Quick Look, which lets you examine a file's contents - be it Word document, PDF, or video - without having to open the associated application.

Simply highlight a file, tap space and you can see the contents of the document or photo. It makes finding files and relevant parts of a file an instant delight.

Within minutes, you wonder how you ever lived without it.

Stacks is a new feature designed to make your folders simpler and less cluttered.

It gathers your downloads, for example, into the bottom right hand corner of your dock. Clicking on the icon - which is the last item you downloaded - opens up a window showing up to 63 of the items in the folder.

Bizarrely, you cannot use Quick Look at this point - as a click on the document or file opens it inside its associated application.

It's a strange lack of cohesion across Leopard's user interface.

And a Stack - which can be built from any folder of files - is only useful if you have a handful of items within it. Any more than 10 and Stacks is patently a waste of time as it looks just as cluttered as it would inside a normal folder window.

Files can now be reviewed using Cover Flow

Another addition designed to simplify your digital life is Spaces. It lets you have multiple virtual desktops, which you can configure to suit different needs.

You can have a Space designated for e-mail and productivity programs, another for entertainment programs and so on.

It is a feature "borrowed" from Linux operating systems and is only really useful if you are a power user and tend to need to have many, many applications open at one point.

Some of the key applications in OS X have been upgraded. iChat has been given a big overhaul and perhaps the most useful feature is being able to share the screen of one of your online buddies during a video chat.

It greatly facilitates collaboration across connected machines and gives consumers access to the kind of remote desktop technologies typically reserved for server software.

With iChat you can also share your photographs from iPhoto with your online buddies - not by sending files but by creating a near instantaneous slideshow.

Mail has been given an overhaul also and is now more integrated with other pieces of software on your Mac.

The Finder, which is the Mac's Explorer, has been given the upgrade it has long needed - and has learned some lessons from Vista.

Users can now see the specific location of every file in Finder with a simple path trail and CoverFlow, so popular with album art in iTunes, now extends to all files.

Instead of boring file names, or thumbnails, CoverFlow lets you see the contents of the file. It's like Quick Look on rails and is a welcome option in hunting misplaced files.

In conclusion, Leopard is a solid release which will please most Mac users without radically altering how they use their machine. For die-hard Mac fans it also does enough to distinguish itself from Microsoft's Vista.

The introduction of Time Machine and Quick Look alone does enough to warrant the purchase.