I'm still kind of a beginner in web design so Bootstrap works well for me...but I do also find myself wasting a lot of time searching sites like bootsnipp.com for the "standard way of implementing this feature", when in fact there isn't any. It also means that I'm not so confident about writing my own code and rely too much on copy-pasting.
The full Bootstrap is also quite heavy—and I notice this more because I'm on a slow Internet connection. It'll probably help if I compile it using only the components I need, but I've been too lazy to do it yet 😛
Still, I find Bootstrap useful to help me finish projects quickly. I'm trying not to get over-dependent on it, though. Right now I'm playing with the minimal Skeleton framework (getskeleton.com) and trying to write as much of the styles as possible on my own.
But, to answer the question "do I use Bootstrap?" the answer is still: Yes.