It has a good upside, but I've yet to use any large framework on a project and not wished I had just reset my baseline, defined a grid, and built everything else myself.

Also, I think frameworks appeal more to dev shops than they do internal sites. Building a frame work for Hightail is easier than using a framework for our marketing and web app sites.

I do have a small WordPress site I'm building for an internal team that will be hosted off-site, so I may try it out on that and see how things handle.