The single most wanted feature in ASP.Net...

Edit and Continue support for Web Application Projects running in IIS.

Until that happens, debugging DNN modules is painstakingly slow or requires hacking your project in order to switch between development modes.

(2.8.2008. A sidenote)
Time required to load DNN is proportional to the size of the /bin folder. That is why I use two /bin folders. A complete one and a small, stripped-to-minimum one. Most module development can be done with the bare minimum /bin folder. However, you have to close Visual Studio when switching /bin by renaming.