Despite the fact that millions of these devices are being build with the same displays, an "universal" calibration file doesn"t always give you a fully calibrated screen. The screens are more or less the same out of the factory, but age differently. If you really want to calibrate your screen as best as possible you need to do it yourself with your own Macbook.
I used
Supercal to calibrate the screen of my iMac, made a big difference. It's shareware so you'll only get a limited version, but this (free!

) limited version is good enough to calibrate your screen decently. Put your screen brightness at the level you'll use your Macbook the most (put it at least at 40%), make sure there are no light sources (windows or lightbulbs) behind you, or do it in the dark, so what you'll see isn't affected by external factors. Then: use your eyes, follow the steps and be as precise as possible when you adjust the sliders during the calibration.
At the end, it'll give you a Colorsync file to be loaded and voila!

That's the way I did it, the result was very good and it was free. A real calibration device like a
Datacolor Spyder offers better results ofcourse, but you can't go wrong this free piece of software.