Is Vim worth the effort?

I'm the bastard child of IDE's and code completion. Would my workflow be faster if I were familiar with Vim?

Depends. Vim is very good at manipulating text, and it cares little whether that text happens to be Java source code or Lisp or what have you. That often is pleasant enough, but stuff like autocompletion that actually has a model of the code or integrated build and deployment scritps were made for a reason, and I see a lot of people spending days configuring vim and Emacs to become half-assed IDEs using disparate plugins, full of UI inconsistencies (vanilla vi   is OTOH very consistent) and lacking integration, thus defeating the purpose of having a both a minimalist environment and of having an Integrated Development Environment.

I personally find that Emacs, with little tweaking, is a very decent C, Lisp (Common Lisp it seems, Clojure to a lesser degree) and L^AT_EX and R IDE, even if they don't work very much the same across languages (the key bindings vary, as well as the capabilities, etc.), so I use it in those instances. For Java, on the other hand, I wouldn't use anything short of an IDE, except for small code snippets but then I prefer using vim for that, if only because it runs nicely on a terminal emulator.

Now, that is of course partly a fault of Java, but the thing is that your needs come first.