Implemented auto-mapper for mapping and converted over the user mappings. Got the gravatar directive working now too. Removed all umbracoUseMediumTrust settings.

src/Umbraco.Web/WebBootManager.cs

@@ -20,6 +20,7 @@ using Umbraco.Web.Editors;
 using Umbraco.Web.Media;
 using Umbraco.Web.Media.ThumbnailProviders;
 using Umbraco.Web.Models;
+using Umbraco.Web.Models.Mapping;
 using Umbraco.Web.Mvc;
 using Umbraco.Web.PropertyEditors;
 using Umbraco.Web.PublishedCache;
@@ -111,6 +112,15 @@ namespace Umbraco.Web
             ProfilerResolver.Current.SetProfiler(new WebProfiler());
         }
 
+        /// <summary>
+        /// Configure the model mappers
+        /// </summary>
+        protected override void InitializeModelMappers()
+        {
+            base.InitializeModelMappers();
+            UserModelMapper.Configure();
+        }
+
         /// <summary>
         /// Adds custom types to the ApplicationEventsResolver
         /// </summary>