I haven't seen this brought up yet (only in some obscure v5 post that was never answered) but what about EditorTemplates. In MVC they live under Views\Shared\EditorTemplates. I've tried to use them but nothing... I'm still new to MVC and Umbraco + MVC but this is something that seems like it would come in handy! 

Edit to add:

@using (Html.BeginUmbracoForm<GD.Umbraco.Controllers.FormsController>("Newsletter"))
{
    @Html.EditorFor(x=>Model)
    <input type="submit" />
}

Would ideally produce my templated Textbox from Views\Shared\EditorTemplates\String.cshtml
Stackoverflow I used to do this : http://stackoverflow.com/questions/5824124/html5-placeholders-with-net-mvc-3-razor-editorfor-extension