It would be remiss of me not to post some thoughts, and for once a little more promptly than I usually do. Mountain Lion dropped this week and I was immediately impressed with the upgrade process, which while upgrading my 2008-9 Macbook Air (pre-SSD) found and corrected a disk error without needing any user input. I have no idea what it was, but the install look longer than the installer predicted and this was responsible according to the installer log. There have been no noticeable ill effects since. My experience has been that previous versions of OS X (and popular competing operating systems) would not deal well with this kind of issue. It suggests that Apple are taking lengths to make the upgrade process as accessible as possible. It required in practice about four clicks and 30 minutes of patience. Good stuff.
On the face of it Mountain Lion looks virtually identical to Lion. There are a couple of extra status bar icons and the dock got a visual renovation that I expect many people haven't even noticed. It looks great, but it's a fairly trivial detail. Most people will have noticed that Address Book and iCal have been renamed to Contacts and Calendar to match iOS, which seems like a pretty sensible move to me, especially with iCloud syncing both of these functions. The status bar now has a few new icons, one is Notification Center and the other notable one is AirPlay (if your Mac supports it) and there's a context-sensitive "share sheets' icon spread about in apps that support it such as Safari.
The two big features of this release have to be iCloud, which now facilitates more of it's iOS features in OS X (notes and reminders most notably), and Notification Center, which centralises and standardises prompts, updates and push notifications in an unintrusive and largely elegant way. iCloud so far works seamlessly. Once your details are in, the compatible apps sync up. I have noticed the occasional delay with Contacts, but on the whole, everything is fine. Notification Center is imperfect; Mail doesn't notify unless it's open, Twitter notifications require manual clearing (unless the native app - that I do not use - happens to facilitate this) and the opening gesture on a free-standing trackpad took a few swipes to get the hang of. On the whole though it is awesome and particularly in the case of Messages is largely discreet - essential on a large screen that might be viewed by friends or family and when a text conversation is often private.
I think Apple's direction is pretty clear at this point, to bring together the functionality of all it's devices so it's convenient to use the one most available for almost any task, without having to be concerned about transferring data or being able to continue working/reading/watching wherever you end up. The hardware should be unimportant (mostly) and the task at hand should be the focus. That doesn't require iOS and OS X to converge, it does require them to co-operate seamlessly with in the limits of their form factor. it requires them to be consistent, and Mountain Lion goes a long way to achieving that.
You don't need me to run down the entire feature list, you probably already know it, and can look it up on the Apple website. I'm pretty pleased with the update though, and can't wait for iOS 6, which is starting to feel like it will 'complete' some of the features (iCloud tabs for example).