The ui-select-match and choices component seems to be hidden behind the div/form structure.
This particular ui-select component is enclosed within several parent elements, including some divs and forms. It eventually renders as follows:
> <ui-select mutliple autofocus="true" theme="bootstrap" style="width:
> 400px;" ng-model="selectedAssignMembers" sortable="true"
> close-on-select="false"> <ui-select-match placeholder="Select
> person..."> <span>{{person.firstname}}</span> </ui-select-match>
> <ui-select-choices ng-style="{'position':fixed, 'top': auto, 'left':
> auto, 'width': inherit, 'z-index': 99999}" position="down"
> repeat="person in persons"> <div
> ng-bind-html="person.firstname"></div> <small> email: {{person.email}}
> </small> </ui-select-choices> </ui-select>