Yosemite and Helvetica Neue
Despite its grand reputation, Helvetica can't do everything. It works well in big sizes, but it can be really weak in small sizes.
I agree that Helvetica can't do everything, but I am one of those that think it fits really nice in Yosemite and welcome the change. I like Lucida Grande as well, but most system text is a lot more legible with Helvetiva to my eyes. Menus look tidier, file lists are clear and so on.