The double-edged sword of code reuse

God yes. Generally working on your own code or project proceeds much more quickly and predictably than working on something "upstream". But it really depends on your upstream. In some cases even moderate changes can be incorporated quickly (i.e. at a similar pace to your own project), but in other cases one is forced to perform major rewrites or take on only tangentially related work, which can be both frustrating and counterproductive to the end users of your own project.

It's really tough to strike a balance between the two; generally I think developers want to improve the projects they participate in, it just needs to be made as frictionless as possible without compromise long term goals for the project so that everyone gets something from the effort.