I am using gwt 2.5 and have the following:

<!DOCTYPE ui:UiBinder SYSTEM "http://dl.google.com/gwt/DTD/xhtml.ent">
<ui:UiBinder xmlns:ui='urn:ui:com.google.gwt.uibinder'
xmlns:g='urn:import:com.google.gwt.user.client.ui'
xmlns:gwt='urn:import:com.google.gwt.user.client.ui'
xmlns:btn='urn:import:com.extjs.gxt.ui.client.widget.button'
xmlns:gxt="urn:import:com.extjs.gxt.ui.client.widget" xmlns:toolbar="urn:import:com.extjs.gxt.ui.client.widget.toolbar" xmlns:form="urn:import:com.extjs.gxt.ui.client.widget.form" xmlns:grid="urn:import:com.extjs.gxt.ui.client.widget.grid">
<ui:with type="com.google.gwt.sample.stockwatcher.client.Resources" field="res" />
<gwt:HTMLPanel>
<div align="center">
<gwt:Label text="Login Demo Using uiBinder" addStyleNames="{res.mainStyle.boldLargeText}" />
<gwt:Button text="Im a native gwt btn, Click Me" />
<btn:Button ui:field="exampleButton" text="GXT button, Click Me" />
</div>
</gwt:HTMLPanel>
</ui:UiBinder>

The native gwt button renders correctly, the label with the injected style renders correctly but the gxt button just shows as text. We are attempting to apply themes to our site and uibinder seemed the way to go. However, we wanted to take advantage of the gxt widgets using the default style without converting and injecting the entire gxt.css. Is this possible?