I tend to avoid Scribd results in Google because most of the time the document is irrelevant when searching for technical terms. You'll get lots of patents, research papers, resumes, etc but not much practical content. I guess it's not really Scribd's fault it just seems like their content is almost never what I'm looking for. I'm also not too keen on the inability to use my browser's built in search-in-page function. Given the choice of a Scribd link or a plain ole' PDF I'll always pick the PDF.