Too Long; Didn't Read
You can do AMAZING sites with plain simple CSS3 - without the use of any external frameworks. Everything in Bootstrap, EVERYTHING, has!important!important. So give goodbye to all CSS rules of Precedence, because you won't be using them. The temptation of making every rule you make just as important as the other is too great. To debug it later, is a nightmare. It breaks the natural order of things, padawan! It's unnatural. So, hear me, and hear me well: forget Bootstrap.