I Wouldn't Buy Yosemite
Yosemite installed as expected on my MacBook Pro (2009) and Mac Mini, as well as my girlfriend's MacBook Pro (2013).
I like the dark menu bar and dock, although some items on the Menu Bar nearly disappear, such as icon for Time Machine. Ya gotta know it's there to use it.
The dark menu bar and dock option is the feature I like best.
The Calculator went from great in Mavericks to rotten in Yosemite. It took a while to stumble onto the icon for the calculator. My first thought was the icom was for Calendar. The icon looks more like a calculator you'd find on an accountant or bookkeeper's desk, not a personal calculator as it was in Mavericks. The Basic option for calculator doesn't have memories. The Scientific option is overwhelming just to get calculator memories. I presume the Programmer option will make programmers happy.
I've turned off and disabled Notifications, don't use 'em.
I've turned off and disabled iCloud as much as I can. Storing my information and files in the cloud where I have no idea who can look at it is not my idea of safe personal computing practice.
Synchronization is turned off too. Each PC (Mac & Windows) I own or use at work, is different. Each has its "personality", such that, I can easily recognize which PC I'm logged into during a Remote Connection or Screen Sharing session. My music is one PC (personal computer). Pictures are on one. All are backed-up on Time Capsule.
The most taunted features over the last few Operating System releases I've turned off for security reasons or it doesn't pertain to my use of personal computers which is why I would not buy Yosemite, and for that matter, I would not have purchased Mavericks.
Leopard was installed in my MBP, I liked Snow Leopard upgrade very much. Snow Leopard was the last OS I liked, and I believe had to be purchased.
I skipped Lion and Mountain Lion because of the abominations made to Contacts and Calendar. If I knew the abomination made to Calculator in Yosemite, I would have skipped it.
One very good feature of Yosemite is switching users is noticeably faster than Mavericks. Thus making Yosemite useful on a multi-user platform.
Overall, I feel like I'm loosing my PC and gaining a very big and heavy iPhone. Dependence on the Internet is not Personal Computing.
From the days of CP/M,
Bernie