From what I understand, AOP is mainly useful for modifying code at runtime that you can't modify before compile time. So for adding logging to your app, meh. For adding logging around a closed source third party lib? Awesome.
Compile time around third party code, or just yours? Because I was trying to extract a point of difference where AOP does something you couldn't do otherwise.
AFAIK - PostSharp modifies your code based on annotations you specified on whole assemblies, namespaces or just classes during compilation to do stuff that otherwise would be impossible
