Well, well... I'm very pleasantly surprised. Sorry Barry, but I've never liked Stellarium as it ran on my PC's (including the QuadCore Q9550) as I found the application jerky and could never come up with a reliably smooth frame rate. It just never felt comfortable and stable.
I've just downloaded the Mac version and have it running on my DualG5 PowerMac on OSX 10.5.8 and its beautiful!!! MUCH better than on my PC's. Smooth, very fast and perfectly stable. Brilliant!