I have to support an elementary school full of Macs, and Yosemite has been my ongoing nightmare. (Well, that and the bad joke known as OS X Server.) I won't update during the year for obvious reasons, but I'm still trying to decide whether or not I'm going to have to fragment my environment again (after just getting it all together with 10.9, finally). The incentive from Apple is very strong to install 10.10, but it just runs like utter garbage on all our older machines. And we can't run out and buy new ones whenever they feel like killing all hardware more than about 3 or 4 years old.

I'm still trying to convince people that our younger kids can learn just fine using the web browser on Windows and that we're overpaying money for these Macs (about double what we'd pay for a comparable Windows machine from our vendors) and wasting our tight budget. But there are a few people who just will not let them go. It's a real PITA running this mixed environment without another person to do sys/net admin stuff, or someone to handle more front-line support.

At this point, I'd take Apple just putting a stop to releasing these updates for iOS and OS X out at the beginning of the school year. It would be so much better if they'd do it about 4 months earlier.