Great article on modifying the ASP.NET compilation. We have updated on this on several systems reporting over slow performance and have seen some good performance improvements using this on a few CRM systems.

http://blogs.msdn.com/b/davidebb/archive/2009/04/15/a-new-flag-to-optimize-asp-net-compilation-behavior.aspx

Inside the CRM 2011 web.config, you can add the statement to your web.config: