I do, for the most part. Am I wierd? I don't feel like I want to waste my limited time by committing to a book that's terrible. I usually go to goodreads or amazon, and take an average of the reviewers, ie. I don't really pay attention to people at either end of the spectrum. OTOH, if I book has MOSTLY bad or good reviews, I take notice. It's stopped me from borrowing/buying/reading books before, and I usually go to the library with a researched list.
I have been wrong in the past. There are books I loved that got terriible or meh reviews, and books I didn't love that got stellar ones (Great Gatsby, for one...don't judge me :P I'm going through a 'reading the classics I missed' phase).
Spoilers don't bother me at all. I guess I'm a 'process' reader, where the whole story arc is secondary to the journey (ie. the actual writing).