Thank you very much, Xantor for a patch that:

Copying, reseting, dragging scripts cause unnecessary recompilation, 
slowing down the simulator and filling up the ScriptEngines directory 
with compiled .dll and misc. files.
This patch keeps track of compiled assets since the last simulator restarts, 
and only recompiles new assets. (editing a script generates a new asset, 
so no problems there).

OpenSim/Region/ScriptEngine/Common/ScriptEngineBase/ScriptManager.cs

@@ -81,12 +81,16 @@ namespace OpenSim.Region.ScriptEngine.Common.ScriptEngineBase
             Unload = 2
         }
 
+        // Xantor 20080525: Keep a list of compiled scripts this session for reuse
+        public Dictionary<LLUUID, String> scriptList = new Dictionary<LLUUID, string>();
+
         // Object<string, Script<string, script>>
         // IMPORTANT: Types and MemberInfo-derived objects require a LOT of memory.
         // Instead use RuntimeTypeHandle, RuntimeFieldHandle and RunTimeHandle (IntPtr) instead!
         public Dictionary<uint, Dictionary<LLUUID, IScript>> Scripts =
             new Dictionary<uint, Dictionary<LLUUID, IScript>>();
 
+
         public Scene World
         {
             get { return m_scriptEngine.World; }