I have been using a framework that I built for over a year and I was able to convert my existing CSS framework in a matter of minutes. I think this will be indispensable in a multi designer organization but may be overkill for those who will be freelancing or solo designers. Myself, I am working with at least two designers and will be hiring more as my company grows and a framework in invaluable of ensuring consistency across projects and for maintenance.
Be warned, for those of you who are hardcore standards literalists and would faint at the sight of anything remotely presentational in the markup Blueprint CSS uses a number of classes that point to presentation in order to build the grid such as .span-6 (referring to the number of spans a particular column runs (sounds a little familiar eh.)
Jeff Croft makes some valid arguments for allowing some presentational nomenclature within the HTML for both production and group production environments most valid being the fact that many of us will never redesign a site without touching the HTML save for those of us building CSS Zen Garden sheets.
I like it myself. A number of points that some people new to the Blueprint CSS framework seem to miss is that while the initial framework is actually large he is recommending using it seperated into the series of files for development and then using one of the compression utilities to both compress the CSS file and move all the content into a single file for live productions. Also people miss the point that the Blueprint CSS is not rigidly fixed to the 50px column +20px gutter. In the comments you can easily see how to change the ratio/column/width relationship.
One of the parts of BP CSS that I have been using since the spring is
Eric Meyer’s Reset Reloaded to eliminate all the browser default styles of the HTML elements. This ensures that you are starting from scratch and not relying on browser defaults to position, space or style HTML elements.
Cheers and all the best,
Jay