I would say go ahead and make some time to finish the book, may as well finish what you started or face the dreaded DNF! ;-p
I enjoyed Born to Run on a strictly entertainment level and steered clear of the pseudo-science for the most part, it was a fun read and the characters and stories are vibrant and uplifting. Simply put, if you enjoy running, specifically ultra running, then it's worth the time. Christopher McDougal makes some grossly overarching statements pertaining to barefoot running in the book and much of it borderlines on sensational- the current barefoot craze wouldn't be the circus that it is today had this book not been released.
Art, I feel the same about "Desert Solitaire" as you do about "Born to Run", there are some nuggets of pure gold in Abbey's words, but much of it slithers along on its belly rather slowly and I'm debating whether or not I even want to finish it.