In any C# application one common problem I noticed is, declare large number of using for namespaces in every .cs files. This has been taken care now by introducing global using in C# 10. Now you can declare common namespace using statements in single file and every file in that project can refer them. No need to declare large number of common using statements in every file.

Read more about global using here. Also there is a good YouTube tutorial on this.

I think this is a very nice feature.