I don't buy nail polish often but when I do it's almost always a color from OPI. They come out with whole new collections that have really clever names that amuse me. But it's the quality of the product that keeps me coming back.
The consistency is really nice and just thick enough that you can get away with just one coat but not so thick that it's hard to apply. It does sometimes thicken in the bottle if I keep it around too long but it never separates or turns funky colors like cheaper brands do.