Using magic strings in C# really unsettles me, so I'm thinking of using the MVC Futures library.
Are there any reasons why I might not want to do this, or any gotchas I should be aware of?
First of all, just because it's a string, doesn't make it a "magic" string. Second of all, I would recommend looking at the T4MVC templates David Ebbo writes about here: http://blogs.msdn.com/davidebb/archive/2009/06/17/a-new-and-improved-asp-net-mvc-t4-template.aspx.
The benefit of this approach is by using code generation, you get strong typing everywhere and it doesn't require compiling expressions which can hurt performance.