I just tried something in Leopard which I am pretty sure I had previously in Tiger without success, and surprisingly it worked. Basically I put my G4 powerbook into target mode, plugged it in to my intel iMac (FW400), and then could successfully boot my imac with the powerbook as my startup disc. So it has basically booted off my powerbook with my mail, folders etc but with the speed, screen etc. of the imac. In my mind at least this would be the ideal way for that slide in docking to work, basically just access the hard drive (which for an ultraportable would be flash based) and use the power of the base machine without worrying about file syncing. I can't be 100% sure but I think I tried this in Tiger but maybe my installs didn't have both the intel and powerpc binaries...? I am wondering if this is an old feature or something new?