I've always felt the exact same way when it came to making a decision on a library - I only rely on what my ears tell me. I got fed up in the past with developers not having enough actual playthrough content and I got angry when I clicked on a review or playthrough video where the person was playing the library like a piano.Listen inside and make your own decisions.
This is not directed specifically at you; however I do notice that some members here spend a cuckoo amount of time asking others about libraries again and again when sometimes all they really need to do is concentrate on already existent walkthroughs. I also have to mention that plenty of libs have "patches only" video reviews that take you directly into the library to judge for yourself. I daresay the latter, when done conscientiously by the video creator, can be even more important toward making up one's mind than the walkthroughs.
I listened to audios, watched walkthroughs and sounds only videos left and right before I bought Studio Brass and Woodwinds. I also read page after page of denunciations. In the end what I was hearing was all that mattered, and what I heard really inspired me. I bought them both and now I'm pleased as punch.
I feel that I would be amiss without mentioning that reviews can be helpful in plenty of other ways besides verifying a purchase already made; they can help you hear and see things you wouldn't have otherwise in order to get as much as you can out of the library.
That's what made me want to make videos in the first place. I never wanted to review libraries, just make interesting audio examples, but I eventually became known as a reviewer. It makes me want to just go back to basics to be honest...