Latest from the Guardian on Yosemite. Not always totally accurate but this app compatibility checker is useful.
Yosemite is the newest version of the Apple OS X operating system for desktops and laptops. Upgrading shouldn’t break anything if you’re already running a recent version of OS X, with most developers keeping their apps up to date, and the Mac App Store providing automatic updates to you. However, it’s always worth ensuring you have a backup of all your files to either a service like Backblaze/Crashplan, and an external hard drive or network drive. You can use Time Machine on the Mac, or Windows Backup Wizard on Windows. Both will automatically back up your computer on a regular basis and offer restores if a hard drive fails. If you don’t have a backup yet, the first one might take some time, but it’s worth it. When you’ve backed up, you can update without worrying – if anything goes wrong, you can restore your files and not lose anything. If you rely on any software, there’s a couple of great tools for checking compatibility before you update, I tend to rely on roaringapps.com (crowd sourced app compatibility charts)