Google Web Toolkit, or GWT, is something that I've been waiting for for quite some time. It is an open source software toolkit that would simplify and modulize UI design and development for dynamic web applications, which so far have been very difficult to write, test and maintain. The confusion over what framework/languages to use for dynamic web programming is the reason that I have so far stuck with the old-fashioned way of static web programming.
The downside with GWT? You have to use Java. It's unknown whether the code written in GWT can be linked with code in other languages such as PHP or Perl. JavaScript is allowed by using the JavaScript Native Interface (JSNI).
Will I start to use GWT now? Probably not. GWT sounds promising, but it's still too early to know whether or not it will become a mainstream toolkit.
PS: A nice, though probably a little bit out-dated, review on GWT: Real-world Experience With GWT on OReillyNet.com (June 2006):
A thumbs up for now. We are still in the early stages of development and figuring things out day by day so I don’t want to claim that it’s perfection or won’t turn out to bite us in some unforeseen way down the road. That said it allows for some pretty compelling application architectures. It really is just like writing a desktop application in Swing or other UI toolkit.
We are generating the entire UI using GWT based on a Controller and IView “screen” or “page” implementations. There is literally *NO* HTML beyond the GWT module import.
That is a very significant departure from almost all mainstream web application paradigms, but if you are comfortable with UI programming it completely abstracts AJAXy/DHTMLy behavior into a very friendly and extensible API.
I guess I would say that if you do most of your web projects with something like PHP, ASP or other template or page-centric language then you may have a bit of a learning curve. If you are already an experienced Java programmer then you’ll probably be able to jump right in without much fuss.