One of the things I sometimes find annoying with intellisense in VS 2005 is that the intellisense drop-down obscures the code that is behind it when it pops-up:

Figure 1

With VS 2005 I often find myself needing to escape out of intellisense in order to better see the code around where I'm working, and then go back and complete what I was doing.  This sometimes ends up disturbing my train of thought and typing workflow. 

VS 2008 provides a nice new feature that allows you to quickly make the intellisense drop-down list semi-transparent.  Just hold down the "Ctrl" key while the intellisense drop-down is visible and you'll be able to switch it into a semi-transparent mode that enables you to quickly look at the code underneath without having to escape out of intellisense:

Figure 2

When you release the "Ctrl" key, the editor will switch back to the normal intellisense view and you can continue typing where you were in the Intellisense window.

This feature works with all language (VB, C#, and JavaScript).  It also works with HTML, XAML and XML based markup.