My macbook pro Core2duo 15" has a secret. . . Well, morely of a feature I didnt know existed. Back on the Powerbook G4 12" I had... If the powerbook is closed and gone to sleep mode, if the battery is removed, the ram is erased and when you put the battery back in and boot up, it must reboot to bring you back into os/x... therefore everything you were doing is gone. On the mabook pro, I THINK that when the machine is put into sleep mode, it writes the ram to the cache on the hard drive secretly before entering true sleep mode. I think it does this while the sleep light is steady, when its done writing, it does the "breathing pulse". When sleeping... remove the battery. Sleep light shuts off, macbook appears to be completely shut down. Put the battery back in, sleep light is still off. Open the lid, hit the power button, lcd turns on and everything that was open is still showing, bit is greyed out, A bezel shows on the screen and very quickly, a loading bar goes across and BAM, you're back to where you were. DOn't know if anyone else has found this out or was pretty obvious... Nice to know it does this for those who are wondering if getting 2 batteries would be a good idea.