The developer experience is a bit complicated, introducing new concepts like aspects and generally requiring you to understand how PostSharp works internally to make it work for you. It required you to frequently cast objects to known types instead of writing fluent strongly-typed intuitive code. Lastly, the emitted code to do something very simple is very complex--dozens of lines of code just to call one line of your own code. PostSharp is no longer free. We have been developing open-source libraries for the past couple of years, and as we prepared to release them publically, we realized that some dependencies on PostSharp made our own open source efforts less appealing. The introduction of Afterthought eliminates this issue by providing a completely free option.