How to decide where to store per-user state? Registry? AppData? Isolated Storage?

When should the Windows Registry be used for per-user state, and when should we use the filesystem, particularly the user's AppData folder? (eg, C:\Users\USERNAME\AppData). Where does Isolated Storage come in?

Is there a pretty firm rule, or is it just a fuzzy thing, like "use the registry until it becomes too much data to store in the registry". or "use whatever you feel like using."

Are there Windows logo requirements that affect the decision?

If I use the AppData directory, how do I choose between Local, Roaming and LocalLow ?

edit: I just noticed these similar questions:

• When and why should you store data in the Registry?
• Registry vs Ini file for storing user-configurable app settings.

I will summarize replies.