Wise needle has taken the guess work out of yarn with there Yarn review section
You can check out recent reviews, make your own reviews or read through everyone elses reviews.
Moral of the post is that you get to review yarns and see what’s what before you commit to a skien.
Not too long ago I did a test knit for another designer that was for a cabled cardigan. It’s really cozy and nice but it just about broke me in a ton of different ways. I couldn’t get gauge, which I suppose is my own problem, but mainly I was somehow both bored and forced to pay attention at the same time.