AutoCAD 2009.
File Format: the drawing file format did not change with this release. The default file format is 2004 format and it has the ability to save back to a 2000 format file. If history repeats itself, this will be the last release on the 2004 format. After all there was 2000, 2000i, then 2002 on the 2000 format. This time around its 2004, 2005, then 2006. Our forecast (based purely on recently history) is that the next release will be called 2007, it will be released in March 2006, and will bring a change in the API and drawing file format.

Interface Changes
The initial appearance of the application is much like previous releases, with the drawing area splattered with all the options. Some long time users find this annoying but it does have a purpose. If new users didn't see these options they might never know they are there. So as usual, long time users can simply click off these options to find the drawing area. Some of these items include: New Features Workshop: This dialog (first introduced in 2005) has a one time prompt for which version you are upgrading from. You can choose many recent versions of AutoCAD or new customer. This allows the 'workshop' to customize its content to show only the relevant information.
Tool Palettes: There are more tabs with more content. The icons are multicolored. These, along with toolbars can now be locked into position to avoid accidentally moving them.
Workspaces: Now you can setup different toolbar, toolpalette, and menu scenarios and save them as a workspace. You can create multiple workspaces for different workflows and change between them with this toolbar pulldown.

Its called Dynamic Input, its definitely different, but not all bad. Here's a screen capture during the line command (cursorsize=100%).

Asyou can see, while dragging you can see the prompt at your crosshair, along with the drag distance and angle in fields. Entering a distance results in a line at that distance in the current direction, similar to previous direct distance entry. Pressing the tab key switches edit focus to the angle, where typing an angle locks that angle in and your able to drag a distance at that angle.

AutoComplete: You can now type in the first few letters of a command then use the tab key to cycle through all matching command names, then press enter to initialize it. Recently used commands can be accessed from a right-click flyout.

Display Transitions: This new option is on by default and transitions your viewport display during zooms, and rotations. For example after selecting a zoom window, the display gradually grows larger until it reaches the new zoom level. The performance hit wasn't bad even on our 134mb topo drawing, but it does take 2-3 seconds longer to complete the display, regardless of the drawing size. It can be controlled with the VTENABLE system variable.

Object Selection: First is object rollover, (like MicroStation) as your cursor passes over an object it is highlighted so you can see which object would be selected. If an object is on a locked layer its not highlighted, instead a small lock icon appears above the cursor. Second is shaded selection windows. If you do a select window or crossing, a semi-transparent shade covers the area as you drag. Controls for rollover in the Options dialog.

Object Creation
Dynamic Blocks: Notice how everything is dynamic in this release? Visibility Options: This allows multiple scenes (or appearances) to be stored in a single block definition. This would allow top/front/side views of 3D objects, as well as differentsizes of objects (such as desks). You could store multiple types of sinks in a single "sink" block.
Multiple Insertion Points: You can define multiple insertion points to aid in placement and rotation of blocks.
Auto Align: Blocks can be defined to automatically align themselves when snapping to geometry. This could be very helpful in placement of doors, sinks, etc.
Hatching: You can now control the hatch origin to prevent bad results with low precision hatches, create separate hatches of multiple objects, and the extents of the area does not have to be inside the viewport. In the properties dialog, the area of a hatch is displayed. The area is also reported by the list command and can be obtained with the AREA command. Hatchedit also has the ability to recreate the hatch boundary (and re-associate it) if it has been erased.
Rectangle: Improved with options. Using area mode you can specify an area along with the length of one side. A rotation option was finally added. After picking the first point you can pick (or enter) a rotation angle, then drag the other corner while viewing the rotated rectangle.