Here are a couple of really worthwhile entries written by Junfeng on the GAC, why you might compile platform specifc and 64-bit... I don't know if I need to bother with my intended GAC entry anymore...

http://blogs.msdn.com/junfeng/archive/2004/08/11/212555.aspx

http://blogs.msdn.com/junfeng/archive/2004/09/12/228635.aspx