Today on IRC someone reported they could not get v3 to work (admin console would not come up). They ran into this error:

    Caused by: java.lang.UnsupportedOperationException: Cannot create XMLStreamReader or XMLEventReader from a javax.xml.transform.stream.StreamSource
        at com.sun.xml.internal.stream.XMLInputFactoryImpl.jaxpSourcetoXMLInputSource(XMLInputFactoryImpl.java:285)
        at com.sun.xml.internal.stream.XMLInputFactoryImpl.createXMLStreamReader(XMLInputFactoryImpl.java:145)
        at org.jvnet.hk2.config.ConfigParser.parse(ConfigParser.java:109)
        at org.jvnet.hk2.config.ConfigParser.parse(ConfigParser.java:104)
        at org.jvnet.hk2.config.ConfigParser.parse(ConfigParser.java:100)
        at org.glassfish.admingui.plugin.ConsolePluginService.init(ConsolePluginService.java:121)
        at org.glassfish.admingui.plugin.ConsolePluginService.getIntegrationPoints(ConsolePluginService.java:423)
        at org.glassfish.admingui.common.handlers.PluginHandlers.getIntegrationPoints(PluginHandlers.java:160)
        at org.glassfish.admingui.handlers.ThemeHandlers.getThemeFromIntegrationPoints(ThemeHandlers.java:98)
        ... 47 more

After spending some time looking into this, I finally found this post after doing a google search (should have done this first):

    http://old.nabble.com/Console-load-error-on-fresh-install-(Cannot-create-XMLStreamReader-...-jaxpSourcetoXMLInputSource)-td26411987.html

Which showed that using JDK 1.6.0_18-ea (at least on linux) does not work with GlassFish v3. Downgrading to the latest stable release (1.6.0_16) solved that person's problem, it also solved the person's problem on IRC.