I managed to get OS X Tiger onto my iMac 5,1 (C2D 2 Ghz). Had to use the 10.4.8 installer to make it work, as the 10.4.6 install had a blocked logo.
Man, I'm so impressed at the speed of Tiger on these Intel Macs. Only, there's a few problems.
For one, for some reason Bluetooth in Tiger breaks compatibility with some of my bluetooth keyboards. It detects and connects to them, but then the key inputs don't work.
Also, there's problems with available software. Since not many people care about Tiger on Intel, there seems to be a general lack of support. At least I have PPCMC and an Intel TFF
– still, TFF can't beat Arctic Fox for speed and compatibility. Arctic Fox can still stream Youtube at 720p from the browser.