I have a 20" iMac and cannot get Tiger running stably. It runs great under Panther with all of the latest updates installed (10.3.9). I have installed Tiger as a fresh install wiping out everything and reformatting the hard drive and zeroing out the data. I have also un plugged all external peripherals and removed the extra RAM however, every time it freezes after 5 to 10 minutes of use or non use. I have now re installed Panther and all is well. One other notable piece of information is that I replaced the internal hard drive with a Seagate 300GB drive as the original one died.
Mani
Mani