Yesterday I asked a question here that got more momentum that what I thought it would. Here is the question link since it is related. I am interested now in the possibility of that using two frameworks together will be worst than using a JS framework and CSS from scratch or the other way around.
The question is clear, if you think there are arguments against using a CSS framework like Blueprint CSS please tell me what you think they are.
The main argument is that CSS is not really a programming language. A framework is meant to include reusable functions and data structures. CSS has neither of these constructs. A CSS "framework" is more akin to a template in a word processor. It provides ready-done design work, but it also imposes more constraints than starting from a blank slate.
Incidentally, this was what drove the development of Compass. It's similar to a CSS framework, but instead it uses the CSS metalanguage Sass, which does have functions and variables. Thus rather than (for example) having columns baked into the framework, you can write something like +columns(5) +column-margins(1em) and it will generate the appropriate CSS.
Browser compatibility? We're continually struggling to maintain IE6 support for the 1/3 of our clients that cannot or will not upgrade. Lots of CSS issues.
I use the YUI CSS libraries, but I'm not sure if that counts as a framework.
YUI handles the basics for fonts, layout (grids) and other formatting and makes it consistent across browsers and Operating Systems. It's under a free software license, also.
They also have a very useful interactive grid designer.