This release of PIX has many significant improvements.
- Draw call timing for single-frame captures—PIX now calculates GPU-side timing information for Direct3D 9 and Direct3D 10 draw calls when performing single-frame captures or during playback.
- Improved 32/64-bit support—PIX has improved 64-bit support and cross-platform compatibility. Run files can be played back on either platform regardless of whether the original application was 32-bit or 64-bit. By using the 64-bit version of PIX to analyze your application, you can take advantage of the larger address-space available on 64-bit Windows and reduce the chance of running out of memory.
- Improved application support—PIX has improved support for applications that call both Direct3D 9 and Direct3D 10. It is also able to safely capture data from multithreaded applications.
- Output Messages tab—A new Output Messages tab is available that better exposes debug output from the Render, Mesh, and Shader views. You can filter messages by view and sort them by event ID, timestamp, and type, as well as copy them to the clipboard.
- Render tab—As you move through the draw calls in a run file, the Render view continues to display the back buffer on Present calls, but for other calls it now displays the currently-bound render target. Also, the status bar now shows the surface format information. In addition, pencil icons appear on all the tabs of surfaces or textures that are currently bound to the device as render targets.
- Buffer Data view—The performance of the Buffer Data is significantly improved and large buffers are no longer painfully slow to examine.
And here's a more detailed article on Gamasutra on new PIX functionality in the June 2008 and August 2008 versions of PIX.