@using SMG.Web.Infrastructure.Controllers.Surface
@model LoginFormViewModel
<div class="login-form">
    @using (Html.BeginUmbracoForm("LoginForm"))
    {
        @Html.AntiForgeryToken()
        <fieldset>
            <legend>Login</legend>
            <div class="editor-label">
                @Html.LabelFor(m =&gt; m.UserName)
                @Html.EditorFor(m =&gt; m.UserName)
                @Html.ValidationMessageFor(model =&gt; model.UserName)
            </div>
            <div class="editor-label">
                @Html.LabelFor(m =&gt; m.Password)
                @Html.EditorFor(m =&gt; m.Password)
                @Html.ValidationMessageFor(model =&gt; model.Password)
            </div>
        </fieldset>
        <p>
            <input type="submit" value="Login" />
        </p>
    }
</div>

Controller:

namespace SMG.Web.Infrastructure.Controllers.Surface
{
    public class LoginSurfaceController : SurfaceController
    {
        [HttpGet]
        [ChildActionOnly]
        [ActionName("LoginForm")]
        public ActionResult LoginFormGet()
        {
            return PartialView("LoginForm", new LoginFormViewModel());
        }

        [HttpPost]
        [ActionName("LoginForm")]
        public ActionResult LoginFormPost(LoginFormViewModel model)
        {
            if (ModelState.IsValid)
            {
                if (Membership.ValidateUser(model.UserName, model.Password))
                {
                    FormsAuthentication.SetAuthCookie(model.UserName, true);
                    return RedirectToCurrentUmbracoPage();

                }
                TempData["Status"] = "Invalid username or password";
                return RedirectToCurrentUmbracoPage();
            }
            return RedirectToCurrentUmbracoPage();
        }
    }
}

The only complexity that I can think of with this application is that I've played around with the UrlProviderResolver and ContentFinderResolver, but I wouldn't think either are involved in Url Routing in this way.