Interesting comment I read on Android Police regarding this new feature:
Originally Posted by Evan Anderson
In order to pick the color for the bars a screenshot must be taken and analyzed. This is done every second to keep up with the current screen state. Taking a full resolution screenshot and processing it is taxing on the CPU, and therefor takes more power, resulting in lower battery life when the screen is on. We are obviously looking for ways to improve this, which is why we released it as a beta.
So don't get too excited just yet and bare in mind you may experience battery drainage.
Samsung Galaxy SII GT-i9100