With something like Eclipse, even adding a little bit of functionality is an undertaking. You have to create a project, write a bunch of boilerplate, load it and so on. With Emacs, it's basically effortless: a line or two of elisp can do wonders. Sometimes I add functionality by just executing elisp directly (with M-:), without even bothering to put it in a file! It's that easy.
This has really changed how I work. Now I don't think twice about having some throw-away elisp for just one project. Or even just one file! Modifying the editor (in small ways) becomes an action almost as natural as copy and paste. Now Emacs is like a jazz performance, with room for improvisation: never the same editor twice.
Emacs is also the perfect development environment for Emacs lisp. (Who would have guessed?) It's the most integrated system I've ever seen; there is an intuitive and remarkably consistent link between the lisp code and the editor itself. I usually know how some bit of elisp corresponds to an action and vice-versa. And if I don't, the incredible interactive help system is, well, helpful: I can easily look up what function a keybinding calls or what keys are bound to a function. These days, I do it instinctively, without thinking. Throw in Emacs's general lisp prowess (paredit is incredible), the ability to randomly evaluate an expression and see the results immediately as well as the ease of inspecting variables and you have a very remarkable environment.
15 minutes as the key to all this? There's no question! Since you're going to be using your editor for years, it's well worth 15 hours or 15 days or even 15 weeks. (And since it's Emacs, you'll end up using it for more than just programming: LaTeX, org-mode, blogging, chatting, email...)
Go for it!