Not so long ago I was fairly happy with JDT's content assist, and then I started using Subwords completion from Code Recommenders project and now it is fair to say that I cannot write code without it! :-)
The idea is simple enough - you should not have to type a name from the beginning to find a match in the content assist popup. It really helps when I do not know if I have to 'find' an element or 'get' an element.
The feature is sophisticated enough to understand a rough shorthand e.g. dclr for declaration.
It is also sophisticated enough to understand that a method or type name in Java is composed of several words e.g. 'ty + dclr' finds all 'type' + 'declarations'.