+ Trying -moz-crisp-edges… doesn't seem to improve speed much on 3.6, and looks worse

+ Created Utils.copy to make duplicating objects cleaner
+ Fixed a number of issues with pulling tabs out of a tray. Temporarily disabled the delay on drag as well.
+ Improved the threshold for switching from grid to stack; only happens when the grid fills up.
+ No longer announcing "bad storage data" when there is in fact no storage data (fresh start)
+ A couple more asserts

browser/base/content/tabview/modules/utils.jsm

@@ -309,6 +309,8 @@ window.Subscribable.prototype = {
 };
 
 // ##########
+// Class: Utils
+// Singelton with common utility functions.
 var Utils = {
   // ___ Windows and Tabs
   get activeWindow(){
@@ -527,8 +529,21 @@ var Utils = {
   },
  
   // ----------
+  // Function: isNumber
+  // Returns true if the argument is a valid number. 
   isNumber: function(n) {
     return (typeof(n) == 'number' && !isNaN(n));
+  },
+  
+  // ----------
+  // Function: copy
+  // Returns a copy of the argument. Note that this is a shallow copy; if the argument
+  // has properties that are themselves objects, those properties will be copied by reference.
+  copy: function(value) {
+    if(value && typeof(value) == 'object') 
+      return $.extend({}, value);
+      
+    return value;
   }
 };