I suppose someone at google started down the GWT path because "write once run anywhere" has been Java's watchword almost since it's inception and a software holy grail since the 1970s. A basic problem with GWT is that it tries to give a java api for building screens which is alien for almost all web designers and front end developers. This means that there is an additional translation from "designer" world into "developer" world.
Because of this, some shops appear to try and co opt java developers and encourage them to build web front ends and this is NOT a good idea. Does this mean a good web designer or user interaction person who knows java (or visa versa) won't be able to make great things with it? Of course not.... But it does NOT mean that a band of capable back-end java developers will be able to suddenly developed a rock star web 4.0 interactive application because "they know java" and "we're using GWT".
In conclusion, GWT certainly has it's place in a capable software developer's toolbox as a mechanism to build screens, but as a replacement for front end developers or some sort of attempt at replacing knowledge of how browsers work, it is a pretty bad idea.