Taskbar? Hell no. The Dock is OS X.
As for the maximise button being changed in Yosemite, I'm not happy. I like the old 'zoom to fit contents' function (I know it's still there via alt clicking or double clicking the titlebar, but it should be the other way around, does any even use full screen?), it makes sense. I've never been a fan of full-screen applications in OS X, it reminds me too much of the days of computers that weren't capable of multitasking, I don't want to go back to that time. It also reminds me of phones or tablets which just make me feel claustrophobic. I wish instead of becoming more like iOS, that OS X would start distancing itself from the horribly confined and limited experience of mobile computing and fully embrace the powerful hardware at its disposal (fat chance, right?).
Also, Notification Center and Launchpad are completely useless. I never use either of them apart from to tidy them up now and again. Notification Center, in theory, isn't a bad idea but hasn't yet been implemented cleanly. But Launchpad is just redundant, the Dock is the primary application launcher and after that its Spotlight, there's no need for a third.
The Finder... I've always had a love-hate relationship with our lights-on-but-nobody's-home smiling friend. While most of the major problems that the Finder had in early OS X releases have been fixed, the main feature that was never fixed/reimplemented is the spatial Finder (older Mac users will know what I mean). This together with windows not remembering their size and position. This annoys me to no end.