I purchased this and some other SRD PDFs a few weeks back, and I haven't cracked a book since. I just bring my laptop to gaming and I'm good to go. I find myself carting a lot less stuff to games, and every book is right at my fingertips. With the search function, I can usually reference info before the other players can flip to it in their books.
Sure, you could download the text SRDs for free, but I feel that having the bookmarked PDF is worth the cost.