Code organization?
Mads brings up the subject of organizing your project. Should you go for a physical schema equal to the way your namespaces are organized? Answer:
It doesn’t matter a single bit.
The fact is that reflection is the way to go from a programmers perspective. The object browser/class browser should be used as your project overview and not your physical files. I know its tempting to start browsing through .cs files but it gets quit messy along to road let alone the fact that your application framework translates itself way better through classes, namespaces other then directories or files. You need to in order to master the application framework to its fullest extend.
Sit down with your team, decide what strategy to use and stick to it. That’s the real issue here. Note the decision is affected by the checkout strategy you use in source control tools (Solution, project or file based? Are files shared across projects or solutions even?).