Scripting Language for an XNA RPG

Yo. I'm working on an RPG engine in C# and XNA. We're planning on targeting Windows and Windows Phone 7, but are running into issues with AI interactions and controlling player actions during cutscenes. FOr the most part, everything is extracted using the MVC design pattern, but obviously would break separation of concerns. So the idea is to have an interface (IScriptEngine) that takes an IScriptObject and updates data in the map model accordingly.
I was thinking about putting the scripts in an XML sort of syntax:
<Script Name="MoveNPC_1">
<Action Command="MoveToTile" Target="NPC_1" Value="10,2"/>
</Script>

And have the engine parse it that way. My biggest fear is performance issues and scalability.

>>15
He's using Cocktothorpe and thought XML was a good idea. He will not be able to write a parser for S-expressions.
I bet even figuring out how the provided XML libraries worked was a considerable challenge for him.