I just finished a small project where changes were required to a pre-compiled, but no longer supported, ASP.NET web site. The code was ugly, but it was ugly before it was even compiled, and I'm quite impressed that everything still seems to work fine.
It took some editing, e.g. to remove control declarations, as they get put in a generated file, and conflict with the decompiled base class, but nothing a few hours didn't cure.
Now I'm just curious as to how many others have had how much success doing this. I would actually like to write a CodeProject article on defining, if not automating, the reverse engineering process.
Will: Due to all the compiler sugar that exists in the .NET platform
Fortunately this particular application was incredibly simple, but I don't expect to decompile into the original code, just into code works like the original, or maybe even provides an insight into how the original works, to allow 'splicing' in of new code.