In large apps I find myself really wishing I had built-in AOP facilities. As it stands in C# the best you can do is factories and RealProxys, PostSharp, ICorDebug, ICorProfi
The May release of Delphi Prism has AOP support at the language level.
You can find out more about it here
http://prismwiki.codegear.com/en/Cirrus
There is also an open source library of aspects from this location
http://code.remobjects.com/p/prismaspects/