A little icon tweaking, a little bigger screen front, a few new icons. A few new option controls for nested files of information. >2 hours to download the 5GB program file. 30 minutes to install it.
Much Ado About Nothing (anyone really cares about).
[Apple: Of course, you did screw up my iCloud account, cause some of my apps to malfunction, and a few other things that were not advertised as being part of the update package. BUT — whether related to Yosemite or not — my iTunes database is performing much better.]