"Nursery school" looks, a first world problem.
Respectfully,
Taz
I wouldn't have called it nursery school myself. That evokes images of Microsoft's Windows XP which had a notable Playskool look to it and was therefore rather colorful as such.
I would say though I don't like the flat look and find Yosemite reminds me of my iPhone in its appearance and I don't like my iMac that way. I'd like the UI to be more attractive and preferably theme-able (I know, dream on) but for now at least I do not see that happening any time soon realistically.
What I most wanted to say though is sure, it certainly is a first world problem and a very minor one at that. Just the same though when you pay a company thousands of dollars a pop for computer systems repeatedly over time not to mention all the other tech from their ecosystem I do think it is fair enough to give them feedback about what you like and do not like.
That said, I also have to concede the majority ought to rule and for all I know in focus testing the majority in substantial numbers liked the new design direction. This assumes they did focus testing but I would expect Apple does this for both iOS and OS X, Apple TV, etc.
I still absolutely love my Mac and OS X in general even if I am not especially thrilled with the aesthetics currently myself. I may elect to use something like Flavours 2 for themes when it releases to put on the pretty face I'd like.
It does not surprise me to see two threads on Yosemite here, one I love it, one I hate it. Nobody can please everybody all the time ever.