Why?
I open my MacBook and think "the menu font is badly aliased, yuck" whereas the Mac Pro at work on Mavericks is still a joy to read.
And trying to work out where a file is within Xcode is still as simple as right-clicking on the titlebar of the window (like all windows within Mac OS) but on Yosemite, how the heck do I do that????? The titlebar has gone!