Once more, John Siracusa has written a massive review of the newest iteration of the Macintosh operating system — 26,000 words of thoughtful and well-written analysis. Below you’ll find what to me — repeat, to me: your needs may be different — are some of the highlights of the review, and of Yosemite. (I’ve omitted quotation marks, but it’s all Siracusa from here on.)

• Yosemite includes a new “reduce transparency” option in its Accessibility preference pane, aimed at addressing possible usability problems created by the OS’s new look. Enabling this option removes transparency nearly everywhere. The Dock, menu bar, toolbars, sidebars, context menus, sheets, Notification Center—all completely opaque.
• The General preference pane contains a new option to switch the menu bar and Dock to dark backgrounds with light text. The command-tab switcher and Spotlight interface also adopt the darker theme, but window chrome and standard controls remain unchanged.
• Notification Center: The contents of the Today view are almost entirely customizable. The day and date cannot be removed from the top (which is a shame), but every other item can be reordered or removed. Individual widgets can be configured by clicking an easy-to-miss “i”-in-a-circle icon that appears in the upper-right corner of each widget on mouse-over.
• Apple is touting Safari’s ability browse the web for two hours longer than Chrome or Firefox on a single battery charge. Thanks to its “native” support for Netflix playback (i.e., without having to install any plugins), Apple claims Safari has a three-hour advantage over Chrome and Firefox when watching videos from this service.
• The second major feature Apple is promoting as part of Mail in Yosemite is called Markup. It provides a way to annotate attachments directly within the message composition window. Any attached image or PDF can be annotated.
• This year, Apple has decided that renaming files en masse is an important enough task that the Finder ought to be able to do it on its own. In the Yosemite Finder’s context menu, just below the option to compress selected files (and just above the increasingly irrelevant option to burn selected files to an optical disc) is a new “Rename…” option.
• The Mac will use your iPhone as a proxy for SMS communication, sending and receiving non-iMessage text messages through it. Both devices must be signed in to the same iCloud account, and there is a one-time verification process to allow a Mac to use a specific iPhone.
• Using a tethered iPhone as the source of Internet access for a Mac is now a lot easier in Yosemite for the common case of a Mac and an iPhone that are both logged into the same iCloud account. (Like cross-device SMS, Personal Hotspot requires iOS 8.1 or later.)