In my opinion they look hideous and take up way too much space (but you may think otherwise). My solution is to have an external battery with me and just plug it in whenever needed. Anker Slim2 will charge the phone one and a half times, is smaller than the phone, and basically the same thickness. Or for more power there's the Slim3 which should give you at least 2 full charges while being slightly thicker than the phone. Built in cable makes it very clean and easy to carry around. Plug it in and put it in your pocket or something.