Are there any tools that would assist us less artistic types in GWT 2.0 layout that use GWTxl? I'm fairly CSS impaired and would like to see how my changes look "on the fly".
Project Vaadin is built on GWT and provides WYSIWYG designer.
There is also plugin for Eclipse - GWT Designer. That is unfortunatelly commercial, but you can try it for free for 30 days.
But to be honest, web making requires knowledge of css - so you should start learning it ASAP - it's definitelly not difficult, just takes time. I've also been messing with those designers (as mostly GUI person) and it was always better when handwritten.
Back to your question, I use GWT Eclipse Plugin and If I am correct, you can see even CSS changes on the fly, can't you?
Free on-line editors for GWT:
http://bootdiskrevolution.com/gwtlab-1.0.2/Gwtlab.html - gwt-lab simplifies the development of GWT Composites. The tool uses a WYSIWYG approach to build the Composite's user interface, including its CSS rules. gwt-lab generates the Composite's Java code to include in the user’s favourite IDE, where business logic and event handling is added.
gwt-lab was developed using: Eclipse 3.4, Google Web Toolkit 1.6.4, and gwt-dnd (2.5.6) for Drag and Drop
http://works.sen-sei.in/gtg/ (GWT Theme Generator) - a simple theme generator for GWT. This application generates a GWT theme based on the color you choose. This application is free for use. No guarantees (implied or otherwise).