I'm not going to go into my specific needs or project setup, but even with 4 open projects, IntelliJ requires 4 open windows! That's asinine when both NetBeans and Eclipse allow me to decide how many projects I want open within a given IDE window. It's the biggest reason I only use IntelliJ when writing IntelliJ plugins.
That setup is so far removed from my day-to-day experience that I'm genuinely seeking understanding here. At most, I typically have 3 or 4 open "projects" at once, and those would be fairly tightly related (like, a server codebase and a couple of clients for it).