As some of you may or may not know, Lukasz Pawlowski and I had presented the deck Building & Deploying Large Scale SSRS farms using Lessons Learned from Customer Deployments (DBA-416-M) at the 2007 SQL PASS conference. In one of our slides, I had indicated inexplictly that "RS runs only on x64 only". I must have been guilty of copying/pasting from some other slides because RS 2005 indeed does work on IA64 (there are many customers that can attest to that). In general, x64 is a more common deployment for RS because it is often less expensive (and IA64 being reserved for SQL). Saying this, yes, RS2005 does work on IA64.
If you want to know more information about Reporting Services, please don’t forget to head to Lukasz’s excellent blog Musings on Reporting Services and Notification Services.