My distant colleague Manju has just published a very well written article on Adobe DevNet regarding performance considerations of running ColdFusion 8.01 on 64-bit Windows (and Mac) platforms. The article gets you up to speed on the basics of 64-bit architecture in practical terms, however the best part is on the last page where he reports on three different ColdFusion scenarios comparing 32-bit performance to 64-bit for cpu intensive, memory intensive, and disk I/O intensive conditions. Its definitely worth a read:

Taking advantage of 64-bit support in ColdFusion 8
by Manjukiran Pacchhipulusu
ColdFusion QA Engineer

At the end, Manju provides a list of credits that helped him develop the article, including my blog entry from last year, Performance Considerations for Running ColdFusion 8 in 64-bit Mode.