Edit: Now that Bootstrap has been around a while I’ve updated my thoughts.
The inspiration for Twitter’s Bootstrap is pretty awesome – a predefined reusable modules for building beautiful, elegant sites. Who wouldn’t want that? There are so many common design patterns we front-end developers use throughout our work, why not put them all into one place?
That was what I was looking for when I decided to build my next site using bootstrap… and it did save time, initially. I decided to use the LessCSS version, I LOVE mixins, and within a couple hours I had 95% of the site styled and laid out. The Bootstrap framework is truly powerful.
Bootstrap does for UI what jQuery does for UX… Potentially.
Until you hit a bump in the road.