I have a license for the Professional edition but I for the most part I just use it as a text editor. So I have to ask, what limitations of the Express editions make them non-viable for big projects?
* Multi-unit testing framework and refactoring support
* Third-party extensibility support
The biggest roadblocks to .NET development/adoption are not toolchain related IMO, they are platform related. If you want to bring up a farm of windows boxes, you're gonna pay.
* Testing can be done through other tools such as Nunit.
* With VS2012, you get extensions developed by Microsoft, such as NuGet.