One very cool feature of Visual Studio 2005 is the ability to install a Trial version, and then upgrade to the full version by buying a product key or boxed copy. Doing this means that the trial version does not need to be removed (wiping out all the carefully-crafted settings for the IDE) to install the full version. This option can be found under the "Add or Remove Programs", "Change/Remove" screen:
This is helpful to me because I have a web site currently on Beta 2, and I want to upgrade to the RTM before going much further. Now I can do this with a 90-day Trial, while waiting for the full Pro version I've ordered to arrive.
The MSDN link describing this setting can be found at http://msdn2.microsoft.com/en-us/library/ms246600.aspx.