I really don't like the new design. The dock bar looks weird to name one thing, also the new buttons, bars and the window design is just ugly and plain (it feels like a Linux flavour trying to look like OS X designed by someone's neighbour's kid) - don't let me even mention the folder icons. Photoshop stalled once but that's the only quirck I've had in the past 2 weeks of using the beta so that's not too bad. Design wise however, I don't feel like this is a good replacement. Have to admit that iOS 7 did grow on me and I felt the same about that back then but I don't think the same will happen in this case.
The dock is more or less identical to the surprisingly ugly (especially on the iPad) dock on iOS 7/8. At least Yosemite offers the "dark" option, which is a considerable improvement.
Meanwhile several Linux desktops have actually incorporated design teams and are starting to look quite beautiful. Never thought I'd see the day where it's prettier than OS X, but today may be that day.
