A massive boon for us has been the ability to rapidly prototype UI concepts for clients. People definitely prefer interacting with tangible objects over flat wireframes. The more complex the UI paradigm you're trying to represent, the more likely you should be using the bootstrap.

That.. hmm.. still doesn't really help me. How do you use it to prototype?

Is there a tutorial somewhere, or someone developing something?

For me, the Bootstrap-101 videos got me from "wtf do I do with this thing" to "oh, I get it now". The pacing was a bit slow for me, but overall I got a lot from the videos.

http://webdesign.tutsplus.com/tutorials/complete-websites/tw...