From the Microsoft Dynamics AX Blogs: AX 2012 .NET Assembly Deployment; Printer Queues; IL Compile; Grants as a Funding Option
AX 2012 .NET Assembly Deployment: Joris de Gruyter favors deploying the assemblies in AX 2012 over those of AX 2009, as his Dynamics AX Musings blog indicated. He explained AX 2012 improved assembly deployment and referencing, especially for clients. He added, "The assemblies don't need to be copied to the client/bin folder."
He warned users to watch out for,