I didn't think of that when writing the parser.  I'll add something like that.  
Maybe <form:value text="{msg.foo}" /> to be more consistent with Buttons, etc

thanks!

After some effort, I am able to get 3 forms of this.

<form:SimpleComboBox
        width="80"
        triggerAction="ALL"
        editable="false"
        simpleValue="item 2">
    <form:value>item 1</form:value>
    <form:value>item 2</form:value>
</form:SimpleComboBox>

<form:SimpleComboBox
        width="80"
        triggerAction="ALL"
        editable="false"
        simpleValue="{issue20constants.after}">
    <form:item value="{issue20constants.before}" />
    <form:item value="{issue20constants.after}" />
</form:SimpleComboBox>

<form:SimpleComboBox
        width="80"
        triggerAction="ALL"
        editable="false"
        type="com.jhickman.web.gwt.gxtuibindertest.client.model.Music"
        simpleValue="{issue20constants.music2}">
    <form:item value="{issue20constants.music1}" />
    <form:item value="{issue20constants.music2}" />
    <form:item value="{issue20constants.music3}" />
</form:SimpleComboBox>

The first one is the one I added last week.  Only works with Strings since it's 
using an innerHTML.
The second and third are very similar.  By default, the item values will be 
parsed as Strings, but the SimpleComboBox can be applied with a "type" 
attribute.  The value should resolve to a fully qualified Class.  In this case, 
I make my issue20Constants music1(), etc return Music type.