We made a number of Dynamic Block and Dynamic Block Editor enhancements in AutoCAD 2010 based on customer requests and feedback.
How many times have you created a new Dynamic Block and then have to save it into your drawing first only to find out that it did not work as you intended it to? Well now there is an option to test the Dynamic Blocks in the Block Editor environment before you have to save it. You can access this on the Ribbon or with the command BTESTBLOCK. 
We added the power of geometric constraints.
Below are two recessed light blocks from the Tool Palette in AutoCAD 2009 and then updated in AutoCAD 2010 with the addition of geometric constraints.
We enhanced the lookup property table making it much more flexible and powerful. Now with cascading menu. You can create a Block Table with the new BTABLE command This gives you the ability to create one block with many different sizes. You can have one block serve the purpose of a hundred blocks.
We added the BCONSTRUCTION command to allow you to create construction geometry in the dynamic Block that will not display when using the block. 
We cleaned up all those action lightning bolts that when you had a very complex block was a real busy mess. Now they look nice and clean. Below is a real world example of the same block in AutoCAD 2009 on the left and AutoCAD 2010 on the right. This block is from Dynamic Block master Mark Douglas of MKM in Santa Rosa who also has a blog In the Dynamic Interface.
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The BESETTINGS command displays the Block Editor Settings dialog instead of in the past with a System Variable.
Even the Block Editor background color changed from that pale yellow plus many more changes based on customer feedback.
We really appreciate all of the customer feedback to improve the products,
Thank You!
Shaan
Is there a way to control the visibility parameter of a dynamic block after it has been inserted into a table>??