Welcome back, Apple. Seriously.

For Windows users, it's primarily the safety of running all their old applications at full speed, or as near to full speed as makes no difference. This is something Apple couldn't offer until very recently - but the transition to Intel chips has gone smoother than anyone expected. And with Intel chips, there's no performance or compatibility penalty that comes from CPU instruction level emulation.

Thanks to Parallels and VMWare Fusion, Macs can even run Windows applications seamlessly on the same desktop. Without these two applications, Windows users can still dual-boot using Apple's own Boot Camp, although a copy of Windows is still needed in both cases. When users have their favourite music or special interest software for Windows, that makes switching alot more attractive.

Leopard does have the usual collection of annoyances and very welcome tweaks we've come to expect.

But Leopard, like Tiger, is about one very major new feature - in Tiger it was search (Spotlight) and in Leopard it's backup (Time Machine). But both are primarily marketing rather than releases - designed to remind people about the Mac system. That's not meant to be dismissive: Apple had done pretty much all the heavy lifting by the time OS X 10.3 (Panther), the first usable successor to the old Mac OS, appeared four years ago.

So on the plus side come lots of very minor but welcome interface improvements: Better parental controls, a Windows-style preview called Quick Look, and simple screen-sharing across a LAN. On the downside, there are one or two UI novelties that seem to be included for no reason other than to confuse and annoy users, such as the translucent menu bar.

As for "Stacks", it's something I first wrote about four years ago when I interviewed one of the original designers; it's a technology Apple has had since 1992. (Read about how "Piles" evolved into Stacks here.) But I'm reserving judgement until I've had a chance to put it through its paces.

Experience has taught me never to judge a new mobile phone unless a full month has elapsed - additions that seem useful after a week or two prove themselves to be tiresome gimmicks after a couple more. Similarly with desktop UI er, "innovations". After a month of Tiger, I'd gone back to CTM's excellent FoxTrot Personal Search for finding documents by content, and Devon Technologies' (free) EasyFind for finding files by name. And it took even less time to unburden my F12 from Dashboard.

But Leopard looks set to fulfil its role as a reminder why the Mac is simpler, more secure and less of an unmanageable hairball than its chief desktop rival, Windows.

We'll have a full preview soon after the Torrent has downloaded Leopard goes on sale. ®