A Slashdot post to a thread called Intel: No Rush to 64-bit Desktop by Epic's Tim Sweeney (thanks GameSpyDaily) makes the case for why developers need cost-effective, backwards-compatible 64-bit CPUs sooner rather than later. Along the way, he offers an update on the status of a 64-bit version of UT2003, along with word that their next generation content tools will required the use of a 64-bit CPU:

Regarding this "far off" application compatibility, we've been running the 64-bit SuSE Linux distribution on Hammer for over 3 months. We're going to ship the 64-bit version of UT2003 at or before the consumer Athlon64 launch. And our next-generation engine won't just support 64-bit, but will basically REQUIRE it on the content-authoring side.