OPI is often considered the golden standard when it comes to nail polish- with a price tag to match. And while this is true for most colors- it is not across the board. Some colors are very subpar in terms of quality and end finish.
The best a person can do is to read individual reviews first for the color they are interested in.
However, I agree that OPI does not stain and they come up with some really cool colors. Look out for the 3 for 2 sales that occur often to help with costs.
The quality of the formula varies from colour to colour and they may be a little pricey but overall I love OPI Polishes. They have an amazing range of colours and textures, are relatively easy to apply to your nails, and don't take a lot of time to dry. My favourite colour has to be Fly from the Nicki Minaj range!!
Tips: If you're using any of the polishes that are extremely glittery, you'll need to use a few layers of base coat to make it easier for you to remove in future. Otherwise, you'll have bits of glitter stuck to your nails for weeks!