This post ties together all the AC9 posts.
Overall AC9 is very much like AC8. Superficially it is almost identical. The changes primarily concern interface and performance.
Performance means it runs faster and better. Interface means:
• Selection is improved. Quick Selection lets you select virtually any element without finding a detectable edge or node. Escape deselects. (Without a deselect function, that QS thing would be a very mixed blessing.) Cmd-Shift restores the old caps lock functionality, letting you 'scroll' through a pile of coincident elements. Objects can have detectable edges. Select with a box under any tool by holding down Shift. To select with a box over a QS-able element, hold down Shift and the spacebar.
• Less switching between tools. The unified pet palettes mean it doesn't matter which tool is active, and the palette commands work better. There are also polyline/polygon editing improvements
• You can switch objects without all the settings reverting to default. There's a search field in the Object (etc.) Settings dialog.
• The Work Environment is much easier to customize, save, distribute, restore. We have toolbars, yay.
Interface changes may seem superficial, but together the whole working experience has been smoothed out and is much more efficient.
There are a few welcome tool improvements. We finally have cover fills on model polygons. The Text tool is utterly transformed. Optional section rebuild is nice, but be careful. Dimension settings is one of those things that's deadly boring until it bites you, so it's good that views now take them into account.
PlotMaker is still PlotMaker, poor thing.
That's all the big stuff. You should peruse the New Features Guide, which is in PDF format on the installation CD, and at 3 Resources : Documentation.