Have you tried just seeing what <% Eval("NodeOwner").ToString() %> resolves to? If it does'nt resolve to anything then all of your statements will be true.
The NodeOwner will also be an integer (the user id), so your logic won't ever resolve false because a number will never equal their names.
If you are using the Full name
<%# (GetUserFullName(Eval<int>("NodeOwner"), -1) != "Britney Spears") ? "Britney Spears true" : "") %>
Or using Text/html
{% (GlobalObjects.Users.Where("UserID = "+NodeOwner).FirstItem.FullName != "Britney Spears") ? "Britney Spears true" : "") |(identity)GlobalAdministrator%}
If you are looking up by Username, use the below
<%# (CMS.Membership.UserInfoProvider.GetUserFullName(CMS.Helpers.ValidationHelper.GetInteger(Eval("NodeOwner"), -1)) != "Britney Spears") ? "Britney Spears true" : "") %>