It's interesting that so many of the comments here (and often, those made about Bootstrap in general) focus on the aesthetic of a few form elements and not the utilities that come with the framework. Understandable, I guess, as they're the most obvious when you load up the page!
I've been playing with the 3.0.0-wip branch for a little while, and I think that there are a couple of really cool features that should be noted above the cosmetic - the single, fluid grid; font icons by default; and a mobile-first design.
I've only been using bootstrap for a week, but I instantly noticed that the grid elements were separated not with a left margin, but with both left and right padding. This is going to be fantastic, and shows their responsive first thinking.
Weird that the Grid section is buried in the CSS section where it's the most important. See, I like that Foundation starts by explaining directly how the grid system works. That columns need to be in rows, etc... Overall Bootstrap's documentation is better, but it lacks this Grid System first approach.
Still no border-sizing:border-box. Which makes me still root for Foundation.
Buuut, there is now a better nesting (Foundation-like) where there is no need to write row-fluid. Which is good.
Why does padding make it more responsive than using margins? I've considered using padded grids as well, but was discouraged because it would lead to more markup if you don't want background images/color to bleed into your gutters.
I've been playing with the 3.0.0-wip branch for a little while, and I think that there are a couple of really cool features that should be noted above the cosmetic - the single, fluid grid; font icons by default; and a mobile-first design.