It will run fair. The Graphics card on the iMac G5 is no standout so it will be okay, but not blazingly fast. The MacBook Pro with the upgraded graphics card and 2 GB of RAM will be much faster.
Thanks, I will just to the make do for now, until I get the Macbook Pro. How will Aperture cope with my original image files residing on a NAS disk array? The access times to the NAS drive are not fast when compared to a fast local disk. I will probably just have to test it out! I have over 1TB of image files from JPEGS, RAW, derivative PSD, to high res TIFF scans of 4x5 and 8x10 film.
The decision for me seems to be down to Lightroom or Aperture for image catalogue and workflow.