I have been using SmartGWT but have run into trouble mixing SmartGWT with other frameworks such as Wicket. Infact it has been a bit of a disaster and I regret going with it in the first place.
I do not want this question to turn into any type of flame war, so therefore would just like people to list alternatives and their experience with those alternatives.
The post above is actually mine, not too sure what happened but I can give you extra resources if you want to take a look at my recommendation. Below are numerous getting started resources that I found very useful.
I would also state that I integrated it with many frameworks and it worked flawlessly.
I did also like working with ICEfaces if you do like the JSF approach, however, that can get rather complex! Personally I prefer ZK’s approach, each to their own.
Hope this helps!