Leopard does do pretty well on G4's. Some are much better than others, and in some cases not well enough for everyday use. For example, I have 2 TiBooks and both are still running Tiger even though one is 867MHz and the other is 667MHz. They still see enough everyday use that I want them running as smooth as possible. The 17" 1GHz iMac is running Leopard since its got 2GB of RAM, but its still not what I would call fast. My 1.5GHz Powerbook smokes through Leopard and I would never see any reason to downgrade. I would assume that just about anything over 1GHz does a much better job at Leopard if given enough RAM and a fast HD. The last G4 in the house running Leopard is my G4 Cube. At 500MHz, 1.5GB and a Radeon 7500, its about the absolute minimum to get it going. Its slow, but I just enjoy seeing such a great old computer running Leopard. I use this thing all the time, but I have to be patient with it. I think your dual processors are what make the difference. With Tiger, my cube scored 22.34 and Leopard brought it down to an 18.43.