I've been using my mum's MPB C2D quite a bit, in anticipation of my own i5 arriving, and one thing that gets on my nerves is the ambient light sensor. It seems to be really sensitive, to the point where it will change the screen brightness when there has been no real changes in ambient light. If you move your hand over the sensor at the top of the screen, or even if someone walks past and casts a shadow it can change for a few seconds. Also, just moving the laptop around and the sensor changes the screen. Obviously this setting can be turned off, but I'd like the feature if it wasn't so sensitive. Other than that, I love the MBP and can't wait for mine!