o.k., it's quitting time here, but what I'm inferring is that the interface may be slow in tiger on a g5 (32-bit) using a 32-bit app and a 32-bit OS, but that it may also be slow on intel imacs, perhaps with 64-bit OS/CPU.  unfortunately there's gonna be no commonality in VRAM nor GPU between those.  all prefs/preview display at default settings?