It's a bit of a subjective question, but I've wondered myself so I will attempt an answer.
Assuming you can integrate it into your product (a separate discussion), Bootstrap will get you to a decent place quickly. I say "decent", because I don't consider it to be the end-all.
Pros
- works in all modern browsers
- "mobile first" approach in version 3
- normalizes many little CSS annoyances
- lightweight
- customizable
- encourages use of LESS CSS (http://lesscss.org)
- gives consistency
- helps aesthetically-challenged developers (although I believe every developer should have a working knowledge of UX)
- many great-looking starter templates available (https://wrapbootstrap.com/, http://bootswatch.com/, etc.)
- integrated with jQuery (some might consider this a negative)
- comes with some jQuery plugins
- some jQuery plugins now offer Bootstrap theming
Cons
Weak when it comes to complex data entry screens. Of course, screens should be made simple for users, but that doesn't mean a form might not be technically complex. Sometimes, users are well-trained and want complex forms so that they can rapidly do work.
jQuery plugins are limited. Certainly, you can integrate your own, find other 3rd party controls, etc. But out of the box, you are missing the heavy-hitters, like grids, tree views, drag and drop, etc.
Naming conventions and semantics are mediocre. Example: using the <i> tag for icons. Class names like "pull-right".
It's very customizable, but inevitably many sites start looking alike (just like Wordpress—consider how many blog sites look the same).
And finally, the great pro and con: it's someone else's code. You didn't write it; if you want it to work differently, you must discover how to do so, and how to deviate from the established code stream.
Case Studies
Here's how I've approached it on several recent projects. All are written using c#, ASP.Net MVC, HTML5, CSS 2/3 and jQuery (similar to the development stack in the question).
For reference, I'm a fairly solid in JavaScript and CSS. If no one on your development team is strong in CSS or JavaScript, starting from scratch will be a daunting task (and probably a waste of time).
Safety/Compliance Product
This product features a complex security model and is heavy on data entry/workflow. The business processes managed by the application are complex, so the chief goal of the UI is simplicity. I started with Bootstrap, but ripped it out within a day because I knew I would want complete control and I already had basic CSS patterns and a handful of JavaScript components of my own to build upon.
However, I kept LESS CSS. I also liked the color-coded buttons. Occasionally (and this is still true), I used Bootstrap as reference to see how a widely-used framework approaches a particular challenge.
I knew I had the luxury of being able to devote a great deal of time to this product, and I made the time commitment to improve my own framework and my own documentation. The deeper I got into the product, the more freedom/extensibility I needed to achieve the UI I wanted.
This product has been commercially demonstrated and sold, and the user interface has been very well-received. I made the right choice by spending the time on my own code.
Online Wizard
This was a simple, public-facing site which collects user information. I designed most of the solution, but I did not work on it full-time.
Initially, using Bootstrap went quite well. In fact, this answer touted Bootstrap as a success before the project was complete.
The team liked Bootstrap and had familiarity with it. They rapidly built a few mockups using a customized Bootstrap template. The resulting user experience was far above average and Bootstrap saved time. The team had no trouble finding documentation when needed.
Digging into the "someone else's code" in the Bootstrap template proved to be challenging for the team, but they managed to strip out the things that were unneeded and make it look acceptable.
Bootstrap took the project through the prototype phase. Once we began to fine-tune, it became much less useful. We never made a decision to "stop using Bootstrap", but by the time the project went live, we had found superior JavaScript components and customized the CSS beyond recognition.
Simple Public Website
This website is purely for marketing and needed to be built rapidly. My customer purchased a template they liked and we customized it in a matter of hours.
The template's code was reasonably easy to navigate. The only difficulty was that it was written for a prior version of Bootstrap.
Is it perfect? No. But it got the job done in a hurry and works well on most devices with very little effort on my part.
Documentation Websites
I have used Bootstrap—100% uncustomized—to reduce the time taken to build professional-looking documentation for online systems (e.g. API docs). For this purpose, I love it. It allows me to provide professional-looking content with zero energy wasted on style.
Conclusion
If you are short on time and/or experience, consider Bootstrap. If you are planning a major product, be prepared that you may need to "dig deep" into the code.
It is certainly possible to use Bootstrap to build a great-looking site. And it is equally possible to do so without. Use the right tool for the job. Investigating Bootstrap as a candidate tool at least once is probably worth the time. Even if you are experienced, you may pick up a few techniques.
Recently I have been hearing from my dev friends how great bootstrap
is, and how to not use it is the pinnacle of foolishness.
Very few technical things (or the omission thereof) are "the pinnacle of foolishness". Take a weekend and try integrating into a part of your product. You will very quickly see its strengths/weaknesses and begin to determine its value.
