I've been using Photoshop CS6 for a while and I have to say that the interface and user experience is a big improvement. Instead of releasing more new tools, Photoshop CS6 put a lot of focus on the basics — the essential tools that we use very often such as crop tool, type, layer group, and save. For example, now you can apply effects on layer group, keep cropped pixels, type styles, and save in background. These simple enhancements result in increase productivity.
Better Layer Right-click Menu
Now the layer color can be set via the layer right-click menu. In the previous versions, it requires 5 clicks to set a layer color (right-click on the layer > click Layer Properties > click on the color dropdown > click to select a color > click Ok). Now it can be done with just 2 clicks (right-click on the layer > click to select a color). That is 3 clicks less!
I think the layer color can be further minimized by placing the color icon horizontally without the color labels. The color label is not quite necessary in this case. So it would be like the Mac file right-click menu.
In CS6, the crop grid automatically activated as soon as the Crop tool is selected (this reduces one mouse drag). The new Crop tool allows you to rotate the image instead of the crop handles. It also introduced some nice crop options such as constrain ratios (16x9, 5x7, 2x3, etc.) which are great for cropping photos for print.
My favorite new crop option is the "Delete Cropped Pixels" checkbox. To crop an image and keep the cropped pixels in the previous versions, you would need to manually edit the canvas size and re-position all layers.
CS6 added transformation values which is very handy. When transforming an object, it tells you the dimension of the object. This is useful when sizing an image on the mockup. The transformation value can be turned off at Perference > Interface.
Searchable Layers Panel
For an average design mockup PSD, it can easily contain more than a hundred layers. Sometimes it is quite difficult to look through the layers. The new Layers palette allows you to filter the layers by kind, effect, mode, color, etc. or search for specific layer name.
Character & Paragraph Styles
For web designers who use Photoshop to design mockups, the new Paragraph and Character Styles is a big thing. Think of it like CSS styles. You can create styles for body text, headings, titles, links, captions, etc. and apply to the text layers. When you edit the styles, it will automatically update the text layers. Not only will this save time, but it also makes your mockup text more consistent.
Layer Group = Layer
Now the layer group is treated like a single layer. This means you can apply layer effects directly on the layer group. Before CS6, you need to either flatten the layer group or convert it to Smart Object in order to do this.
Photoshop CS6 now allows you change blending mode, lock, layer color on multiple layers. You couldn't do this in the previous versions. Also, in case you are not aware, now you can use Cmd+J to duplicate multiple layers.
Auto Save & Background Save
Finally, auto save in Photoshop! No need to worry about software crashes any more. Beside auto save, there is a new background save. This means you can still use Photoshop to work on file while another file is saving. This is particularly useful for editing large files such as large size illustration or print design. The auto save and save in background option is available under Perference > File Handling.
There are new features in Photoshop CS6, here is a good video that summarizes everything.