So what is that new feature of writing nodes all about?
One way to look at it would be that we just added c# language support to your favvvvorite developing environment. Because even if you might not see yourself as a developer, you still are already programming: up to now you do that visually. And you are already building your own nodes when patching subpatches or modules.
So from now on you just have more possibilities on how to create new nodes: patching visually or writing textually.
To not be forced into the terms visually, textually, vvvv node or c# node, we are still sticking to the terms patch and plugin. A plugin simply is a node written textually.
The new thing is the way how you can write plugins: dynamically within vvvv, which should ease the way of getting into c# programming.
Now why would you want to use c#?
Firstly there are programming tasks, that are easier, faster or more performant to do in c#, because each programming language has its strengths and its drawbacks. Additionally there are still things that you can't do with patching (like using some powerful .NET libraries and calling its methods directly)