...killer feature but one that eventually people won't notice.
The idea is simple: if an application crashes or is shut down without saving, the application saves the latest version of the document automatically. This safeguard is massively useful but requires a compliant application. Apple's iWork suite works beautifully here.
The same applications now save all versions of documents so you can scroll back in time, just as with Time Machine, to find that killer paragraph you accidentally deleted weeks ago. Yet another feature that will probably be taken for granted in the future and on other platforms.
Full-screen apps look great, especially on a smaller 13-inch screen where window clutter is often a problem and where space is at a premium.
In addition, Lion's new Mission Control feature - see below - also comes in handy here.
As well as the visual clues from iOS, the other big nod towards the Back to the Mac concept in Lion is in touch gestures.
Apple introduced a number of gestures between Snow Leopard and Lion. These gestures are supported by various Apple devices including notebook trackpads, stand-alone trackpads and mice.
iOS is, of course, all about touch and eschews the stylus approach. It's all about getting hands-on with the software and it pays dividends by delivering a more inclusive user experience with a device. Apple's hoping for a similar pay-off with Lion.
The number of touch-based interface commands in Lion has grown since the last OS iteration - indeed, there are now so many that remembering them all is a challenge.
Just before updating to Lion I'd splashed out on one of Apple's Magic Trackpads - basically a four-by-four-inch smooth trackpad that lets you perform a number of touch-based gestures.
Before that I'd been using the rather splendid Magic Mouse, which is now paired with a MacBook Pro. Using Lion across both machines with both devices, it's clear that the OS benefits from having the wider area for touch commands. The Magic Mouse's commands are also slightly different to the trackpad's and switching between the two computers can be confusing given the wide number of commands available.
But it's clear that using the trackpad with Lion's range of commands is easier and more fun than using the mouse, which can be fiddly. At the same time you need to be more alert to resting your fingers on the trackpad as errant finger brushes can jump you into Mission Control or another screen accidentally.
That said, it's something of a revelation for a day-one iPad user to share some of the user interface elements of the tablet with the Mac. I think this part of the Back to the Mac idea will be most fun to play with over the coming months.
Low points for Lion
Despite the flourishes and interface delights there are also some issues with Lion.
Performance is not what you'd expect, something that a number of friends and colleagues are reporting. Performance is patchy despite running cleaning scripts and executing a top-to-bottom purging of system caches.
Safari in particular is testing the patience despite a number of useful new features. Normally I can blame Virgin Media but they've resolutely provided me with 20Mbps of download access for the best part of the week so the blame is on the software - the hardware is relatively new.
In addition, I've noticed a number of strange buggy incidents. Three or four times I've opened an application only to be sent inexplicably back to the system's login screen.
Every new OS has bugs and no doubt most will be sorted out in coming months with software updates from Apple and from third parties making their applications more Lion-compliant.
Despite the odd bug and occasional system lag, Lion is a real treat for Mac users who, let's face it, haven't been the main focus for Apple in recent times. Lion has a new ideology, a new look and a whole new bunch of features to play with. It also has the familiarity with iOS which continues to help lure new users to the Mac platform.
Yet you feel it is only part of the story. The Mac is now just a device and not the centre of your digital world, according to Apple.
We won't be able to assess whether this view holds true until iCloud launches later this year. By then we may get a better idea of how the Mac fits into the company's vision of a Post-PC world.