Hi, Markus,
I wasn't able to find a reply option on your blog, so hopefully you won't mind feedback here.
When I read your blog, my immediate reaction was the same as Bonnie Berent's - many .NET developers subclass the Winform controls in one class file. To do otherwise (separate class file for each control) is less efficient. I'm not sure if this is an example of your reference to "inner classes", maybe you can clarify that.
Also, I didn't understand the statement "editors can not handle multiple classes in a single assembly", maybe you can elaborate on that as well.
I agree that breaking things out has many benefits (especially in a multi-developer environment). Sometimes it boils down to a level of consistency and being able to explain the approach. At any rate, I'm very glad to see this blog, I look foward to reading more, and I'll be happy to participate in it.
Thanks,
Kevin