put a Seagate Momentus 7200.3 250gb drive in my early 08 MB. I have noticed no problem with power consumption or battery life. BUT I can hear it if I put my ear within 6 inches of the keyboard (old 5400 was silent) and there is a very high freq vibration very noticeable on the working surface of the unit. You just feel it through your fingertips. Not a huge deal, but I didn't expect it.