Visual Studio Express Editions are one of the biggest present that Microsoft has done for the developer's community.
You can have all the power of Visual Studio environment to build your applications for free (the last offer permits you to download all the versions without charge until the 6th of November, 2006 plus some benefits) and you can use all the Express products for building commercial applications. This is a big advantage for hobbists or developers that can't permit to buy the more expensive (and powerful) Professional suite.
The "Express" are always more a must to have... 