I have the Boye set and a few pairs of the Knit Picks options. I have mixed feelings on both.
I think I have only had the Boye unscrew once or twice, and that was only when I was too lazy to use the key thingie to tighten it properly. That being said, my Knit Picks needles unscrew almost everytime I use them, even if I use the key thing to tighten them properly.
The Boye cords don't flex anywhere near as well as the Knit Picks cords do. I love the Knit Picks cords because you can use them for magic loop.
I find the Knit Picks needles are very smooth, pointy and slippery (which I like) and the Boye needles are smooth, pointy, but not near as slippery as Knit Picks.
Overall, I like the Knit Picks Options needles most, but haven't bought the kit since there aren't many small sizes
and I don't use large sizes very often. I've just bought the sizes I use most and a few different length cords and I'm satisfied.
Oh, I also have a pair of Addi Turbos too, and I love them.