If you want strict MVP, I'd suggest using GWTP,
http://code.google.com/p/gwt-platform/. We exclusively use this at Arcbees.com. You can build presenters and child presenters. But with MVP there is some additional overhead that takes place to conform. I don't always dig the additional over head so I don't follow it strictly myself.
For me MVP is not always the solution needed for the challenge, but thats my take on it. I've been building my current projects with MVP using request factory activities and places just fine but like I said thats my take :). For me the UiBinder is enough and with deferred binding you can do some nice separation between the views.
Brandon Donnelson