Set aside any consternation at the continued adaptation of features from iOS. The best thing that Mountain Lion borrows from its leaner, mobile sibling is undoubtedly Notification Center. When you're swamped with meeting alerts and emails all day long, it's a convenient way to filter out some noise, while remaining in touch with people who matter.
Sometimes the simple ideas are the ones that take you by surprise. That's certainly our view of the Share button, which is an efficient way of getting things done without dragging things from the Finder. It's a particularly good point if you use a trackpad.
Apple's efforts to tidy up some of Lion's messy attributes haven't gone unnoticed. The restoration of Exposé-like organisation in Mission Control will appease some, as will the ability to once again show contact groups and a list of calendars on the left-hand side of the eponymous apps. But these are capabilities that should not have disappeared in the first place.
Apple's insistence on a minimal file system in iCloud is fine if you only author the occasional document, but the simplicity soon becomes awkward when you have to deal with many of them. In stark contrast to the Share button, it makes a long-winded job of doing things with different types of document. Apple's determination to avoid a complex folder hierarchy would be laudable if search options worked better (folder names are excluded), and if there was a quicker way to gather related files of any type into a project.
We're also disappointed that icons in the Finder's sidebar are steadfastly monochromatic. Without a lack of colour as a guide, it inevitably slows you down. And iMessage needs improving to better handle file incompatibility when sending from a Mac to iOS device.
If there's one feature that makes it worth upgrading, it's Notification Center. At £13.99, Mountain Lion is a real bargain for that alone. The true cost might be higher if you have to upgrade from Leopard, or upgrade any of your applications to make them compatible.
The rearrangement of Notes and Reminders into their own apps is very welcome if you also use an iOS device. And the swathe of other minor tweaks around the system are positive as a whole.
Apple needs to rethink iCloud document libraries before we're willing to start putting work online. Using iCloud to store documents is entirely optional, and it can be supplanted with alternatives such as Google Drive and Dropbox, which offer a more flexible file system.