I really dislike the fullscreen behavior in Yosemite, not only for the animation (as you mention), but also because I feel like the average user is going to want a "maximize" button more often than a "fullscreen" button.

Besides, most sites that have content that lends itself to fullscreen mode (e.g. YouTube) allow you to enter fullscreen mode through the site, so being able to enter through the browser window is not typically necessary.

At work, I use multiple displays, and it's really not seamless when you have one display in fullscreen mode and another not. Imagine having three monitors side-by-side, with the middle in fullscreen mode, and trying to drag a window from Display 1 to Display 3. Maybe this is fixed by now, but in beta, Yosemite sometimes let the fullscreen mode "overrule" the window dragging, so you couldn't see it on Display 2. I know, first world problems, but it's jarring nonetheless.

What's especially frustrating is that there doesn't seem to be a built-in "maximize" function anywhere! The closest I've come to in Chrome is Window > Zoom, but there's not even a keyboard shortcut for that.