I have two sets of the 6-pack Neutrinos. I bought them because they were some of the first biners I saw to come color-coded--and the anodized colors perfectly matched my BD cams.
My biggest grief is that the non-keylock nose sticks fairly often. It's pretty annoying but not enough for me to give them up and buy different racking biners (just enough that I wouldn't recommend them to others).
They're also a little heavy for such a tiny gate-opening. The gate action is fairly stiff but not discouraging. I tried a few as alpine draws but that provided a disappointing experience too; the Neutrino specialty is definitely cheap-color-coded racking.
They're pretty thin, which is a plus for racking. Though if I were to buy racking biners today, I would buy a different model (willing to spend $1-2 more per 'biner to increase the handling), since there are so many more options now.