At least in my little corner of the front-end dev community, CSS frameworks are considered helpful in some cases, but not a good fit in most cases.
One of the situations where they can be really helpful, though, is in developing a functional prototype. The code is going to be a bit bloated, but most of it is meant to be thrown away in any case.
Actually, I would answer that question with "Compass". Blueprint, etc. are CSS templates and themes, not a "framework" as used in computer science and else where.
Bloated as because CSS frameworks are, essentially, based on CSS and works at mercy of the browser; true “frameworks” like Compass are pre-compiled and comes without presentational classes, therefore less bloat. On the other hand, front-end work is dirty by nature, and I’d argue that a beautiful page with bloated code is better than a not-working page with very clean code.