Only concern here is when you do stuff in parallel it is possible to grab the locally built packages from a different project that restored them in the global nuget cache, and cleaning all *-dev packages in global cache takes more time than in just .packages.

This is probably concern mostly for Playground. Integration tests would have to restore to some local cache anyway most likely (afaik testfx does it that way as well).

But it is probably livable, since other projects do it that way as well.