Using Bootstrap to Refurbish Old Websites: Lessons Learned
whattofix.com
whattofix.com
Here's the link if you haven't seen it: http://twitter.github.com/bootstrap/index.html
The site itself is a demo of how a Bootstrap site should look. There is also a comprehensive list and explanation of all the nifty Javascript's they support by default.
There's a link to download all of the files from Github from that site as well.
That's not necessarily the case. Check out the section "Built with Bootstrap" in the page you've linked for some examples of this.
The Bootstrap site is a good start if you want to get off the ground quickly, but you're much better off in the long run putting in the required time to actually create a design of your own.