When it comes to CSS and front-end frameworks in general, I used to avoid them. I used to favour my own custom solutions because I understood them better and I could include what I needed and not include what I don’t.
It wasn’t until recently when I started a new job where they favoured and had built an application using Bootstrap, did I learn to stop hating it. In-fact, after understanding what Bootstrap is and isn’t, I’ve grown to actually enjoy using it. I see the value in Bootstrap and other frameworks like Foundation.
You already use frameworks/libraries
You use jQuery (most likely) and you’ve probably used jQuery UI before, Bootstrap is no different. You get a set of components and pre-styled easy-to-theme elements (forms, buttons, headings) to make mundane and repetitive tasks a little easier.
Mobile-first Responsive Grid
The big draw card with Bootstrap 3 for mne is the mobile-first grid system. The framework is mobile first out of the box and encourages anything outside of a media query to be for mobile devices and anything within its respective media query for tablets, laptops and computing devices. The helper classes which are handled automatically mean your apps collapse down to mobile with ease.
You don’t realise just how good the grid system is until you witness the classes in action. You can combine different classes to make the 12 column grid system respond differently. By default using the col-md-(number) class, so for example col-md-6 when the screen gets below that of a desktop size (992px from memory) they will shrink and eventually stack.
Form Styling for Scaffolding
If you use something like Rails or Laravel and use scaffolding for form generation for CRUD operations, Bootstrap’s out-of-the-box form styling is a life saver.
There is nothing wrong with using a framework like Bootstrap, you still find yourself overriding its defaults and adding in your own flair at times, but there is no denying it saves you a lot of time and effort solving browser quirks. It’s the jQuery of front-end development.