Mac Yosemite and Mavericks
 

A minor thing - but I liked the little icons on the bottom of the screen for the Mavericks programs a lot better than the Yosemite ones.

Mavericks maps also had a "composite" function that seems to have disappeared with the Yosemite "upgrade"

I haven't upgraded to Yosemite…still have Mountain Lion. I hate losing the things I like in the name of progress...