I'm using Leopard on my MacPro 8 Core to run LR 1.3, PS CS3 and printing to my Epson R2400 either directly from the applications or by using ImagePrint 7 RIP. All seems to be working fine at the moment although I am only a recreational user.
The only snag with my Leopard upgrade remaining is that I use an Eizo ColorEdge CE240W display. The Eizo monitor calibration software, Color Navigator, does not load properly. According to Eizo, the last profile is what is being used, however, I will not be able to update the profile until they release a Leopard compatible version of their software.
Bud