There are some things a designer will throw at you that are very very difficult to achieve in CSS in any regular way (sans non-cross-browser-compatible hacks). But for the most part, CSS isn't too bad.
I've yet to run into those, but then again I am my company's primary designer, as well as implementing whatever I design. Perhaps as a product of that, I don't end up having to code up (m)any ridiculous designs.
I believe that's your answer. When you work with print designers who have moved to web design, but don't know thing 1 about css or html, you get some funky designs.
Really nice designs, but complicated PITAs to actually develop
