It has been found that Xbox 360 consoles manufactured in June 2007 and beyond no longer have the buttons on the side of the power brick plug that require you to squeeze them in order to remove the plug from the console. Such a move seems to have been conducted for cosmetic reasons and not to improve performance of the consoel in anyway.

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This isn't really anything really groundbreaking, but I found a post on the Gamefaqs message boards stating that new xbox 360 power brick plugs no longer have the buttons on the side that you have to squeeze to remove from the console. Two other members have confirmed the existence of the new plug, with one stating his console was manufactured in June 2007, and both stated they purchased Elite consoles.

I'm guessing this is merely for cosmetic reasons, and to make it easier to unplug the plug from a 360.