I wish they would come out with an alti-vec accelerated client for OS X. It would definitely speed things up for my Mac clients. They're getting wasted by my cheap-o Dual 1.3 ghz Duron computer at home. That thing kicks serious butt.
Heck, next year when we start moving to OS X on our workstations (mainly labs) it would be nice to have a hidden client. I used to have a hidden client on dnetc for OS 9, but it slowed the computers down a LOT. X would definitely multi-task better. I've got 120 eMacs I could throw it on here. Shoot, I've got about 1,000 G3's and higher here, but they're all running 9.