Well, I just wanted to post to let people know about some compatibility issues with mixing Crucial and Apple RAM in their Macs. I spoke to a guy over at Crucial who told me that JEDEC SPD standards on the way the memory chips are manufactured changed and could cause compatiblity issues when mixing with Apple RAM. He didn't mention when the change had occured, however I had difficulty in adding an extra 1GB (installed in matched pairs 512x2 from Crucial.com) to the original 512MB (installed in matched pairs 256x2 from Apple). So, if anyone is planning on getting the base 256 upgraded on a new PM (from Apple) and then adding more RAM from Crucial, let this be a warning. It's a good change that you won't be able to use the base RAM you receive from Apple.