New Interface

Collapsible Palette Panes. The palettes can be docked, minimized into icons, etc.
Toolbox as single column or the standard 2-column for those of us who resist change.
Improved Fullscreen mode. (Just press F toggle through em).

Speed

The startup time has been reduced, the brushes respond quicker and the interface is more responsive - yeehoo!

Check out the specs published by Adobe below:

Adobe Bridge 2.0

New updated interface.
Better controls/visuals.
Improved previews.
Loupe Zooming
Get Photos from Camera
Previews of multiple file formats (PSD, tiff, jpeg, gif, png, pdf, ai, eps. flash, etc.)

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Smart filters (more wonderful non destructive editing)

Filter can now be applied in a similar way as adjustment layers - very cool!

Quick Selection tool

Intuitive paint on selctions that can be refined, modified, etc.!

Refine Edge

Making selections better!

Vanishing Point 2

Supports multiple planes

Auto-Align Layers

Panos, composites, and more. Easily combine multiple photos with various settings.

Auto-Blend Layers

Blend multiple images together and blend tone and exposure.

Merge to HDR 32 Bit Imaging

Improved merging of multiple exsposures.

Black & White adjustment

Finally, a solution to all those bw conversion techniques. This is one of my personal favorite improvements.

Curves updated

Excellent improvements here - histogram has now been added, channels overlays display the changes to each channel

Brightness/Contrast

This used to be a feature to overlook except for graphic effect. Now it work more like the equivalent in Camera Raw, and the results are stunning.

Two New Blend Modes

Lighter Color and Darker Color blend modes.

Clone Stamp tool

New Source Palette. You can now make samples of 5 different sources, these can be from the same document or from multiple documents.

Eyedropper Tool – sample sizes

In order to respond to increased file size this now includes 11x11, 31x31, 51x51 and 101x101

Camera Raw 4

No longer limited to Raw files, we can now open jpg and tif files in ACR.

A ton of new and needed adjustments here. Parametric curves. Recovery and fill light sliders. HSL sliders. Split Toning.

Enhanced printing

Let's just say this is a ton better. One-stop printing, better color management, etc. You'll have to check it out.