[michaelneale]

Yes I have used it a fair bit to write javascript - in some ways it provides the boring bits of stuff around js (like module-like systems, name spaces etc..).

If you like IDEs, IDEA from jetbrains even knows when you are doing inlined JS and assists you as you code.

I thought I would hate GWT by now, but its one of those things that mostly stays out of my way. Would I used it for a new project from scratch? Not sure... maybe. There are lots of other options now for more classic web approaches that dont' require it to be a monolithic ajax app (and jquery is pretty hardened to provide a lot of the glue/lubricant).