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
Romain's answer covers (almost :) perfectly the current solutions. As for the future support, Anders Hejlsberg has previously stated that they'were in wait & see mode about AOP.
We can only hope that with the managed rewrite of csc, and a «Compiler as a Service», one could plug into the compiler, and inject aspects there.