This post will mostly be about one thing I dislike about the new Ubuntu theme. So first in short what I like about it. I like the general direction its going, the style, the ideas behind it. I hope it continues that way. Also I can see how this theme can very well evolve into a Gnome Shell theme later. I think it will look great.
Now on to the more fun part. The thing I dislike on whats currently there. I'm referring here to the screenshots found on the official Ubuntu site at the moment: https://wiki.ubuntu.com/Brand
As a lot of other people already wrote, what I dislike the most is the new style and position of the window buttons. Most people take the most obvious route of claiming that the position is plainly wrong. They are on the top-left corner just like in MacOS. I think this is the wrong position, as Mac has it wrong but I can see why Mac is not going to change that. MacOS has a lot of beautiful things and a very good design, but thats one of the areas where they are wrong. Ubuntu's design makes the buttons even worse than Mac.
The wrong position is not my major complain. I used a Mac a couple of times. I'm not used to it and will not claim that I am. I only use them rarely, as I think most users do. That's why I don't care too much about the position, I just think its wrong because they are now on the most prominent and important spot on a window. And this is just wrong for their importance.
In my opinion this is one point where Windows got it completely right. The most important things on a window are the window Icon and the title. This should be on top and left. The buttons to control window states aren't as important. They are even less important than the window content. So positioning them up there is just wrong. Windows has them there rightfully. The title of a window usually isn't as long and that corner would just be empty wasted space most of the time. So putting these buttons there is a good, space saving thing.
Mac is wrong for the same reasons. But they applied some very good design to them so they doesn't stand out too much.
Now Ubuntu does one to me even more bizarre thing. They make these buttons stand out way too much. It even distracts from the window content so much that I notice it anytime I look at a window. In my opinion they can even let the buttons be on the left if they think that improves anything. But they should definitely change the highlighting of these buttons. If the theme stays as distracting as it is now I have to change the border style. I just find it too distracting from the rest.
This could be fixed by removing that ugly "container" border for these buttons. It is of no real use and removes edges from the design which is always a very good thing. Also they should only color the buttons as you hover them. Right now it just makes them too important. The same is true for the Scrollbars I see on these screenshots. Way to highlighted for an unimportant thing as a Scrollbar. They stand out too much compared to the rest.
Also they didn't fix the flawed window border from the old theme. It's still way to small to be usable for resizing the window. The new Windows theme makes this beautifully. There are a few Gnome themes which do this as well. As long as the window is not maximized there is a thick border so the border is easily dragable. As soon as the window is maximized it disappears. But I think that may still change as the theme doesn't look finished right now. At least I hope they still fix a few things till the release of Ubuntu 10.04.