In SQL Developer 4.0 EA 1, if you right-click on a PL/SQL object in the schema treeview, like a function or package, and choose Run, the "Run PL/SQL" window comes up, but it doesn't have anything in it.... This appears to be a bug. I get the same result whether I try to run an object in my schema vs. another schema. Please look into that.
Somewhat related to that.... If you open the PL/SQL object that you want to run (by double-clicking on it), you can then click the Run button in the object window's toolbar, so that Run button still works okay. But, if you use that button to run something in a package, the "Run PL/SQL" window's "Target" list lists the package's functions and procedures in no particular order - this makes it very hard to find what you want to run. Can we get that list of functions and procedures in the "Run PL/SQL" window alphabetized, please?
A known issue and already addressed for the next update.