There is no doubt in my mind, that ASP.NET is the most powerful and versatile platform for web applications at the moment. By leveraging the .NET Framework you can do absolutely anything in no time, but is that power also the problem with ASP.NET?
In the dark ages before ASP.NET, we were stuck with ASP and PHP but we were just as enthusiastic about them as we are with ASP.NET now. They were relative easy to learn and to learn well enough to do something really cool with in a short period of time. That made them accessible to almost anyone with just a will to learn and in my opinion that's what made the web what it is today.
ASP.NET changed all that. The power and scale of it was so immense that it could take years to be familiar with just the page life cycle or the basic classes in the CLR and even longer to be able to take full advantage of the entire platform. After almost 5 years I still find classes and methods I didn’t know existed. That makes ASP.NET much more difficult to learn and master than ASP and PHP.
The tools used to build ASP.NET web applications, Visual Studio, Visual Web Developer Express and Expression Web Designer, are also much more advanced than the earlier tools. The traditional webmaster now has to be a full blooded programmer just to be able to open up a user control's code-behind file to add another item to a DropDownList. HomeSite, TextPad and Dreamweaver 4 were much easier and simpler at the time for editing ASP and PHP files.
My point is that the very essence that started the dynamic web is missing out on ASP.NET because it is too difficult. The hobby web developers and the newcomers face a much steeper learning curve, which might lead them to choose another platform. I believe in the power of ASP.NET, but then again, I’m neither a hobbyist nor a newcomer.