I can :-)
I forked the gwt-comet some time ago in order to bring GWT support to the Atmophere project.
The project has evolved in its own way since the fork and in its current incarnation (gwt20) its is fully based on the Atmosphere architecture, both serverside and clientside.
I believe the owner of the gwt-comet project is not as active on it anymore as he has been in the past.
Using the Atmosphere extension means embracing the Atmosphere project, but its well supported by the owner/lead of Atmosphere.
Hope that helps you