Now the million dollar question is does the MBP EFI know how to use CL5 Ram ?. It might be coded to handle CL7 at best. I believe the older MBP cannot use faster RAM as its EFI has that limitation. Would that likely be carried forward ?.
Some can test it by buying the Kingston CL5 and installing it then boot XP or Vista and run CPU-Z to check the exact RAM timing. I also believe it will run Command rate T2 rather than T1 as well for 4GB. This is a bit slower.