When I designed Code Beautifier Collection I knew it was easy to install it. Just copy the assemblies to a folder and add a registry item under the BDS tree.
However, when I install a Visual Studio addin, usually devenv.exe will execute for a long time and consume a lot of memory. I have to say it is not convenient but there must be something under the hood.
I do not plan to write an addin for Visual Studio, so I will not go any deeper, but I think in this aspect, BDS has some advantage.