This is my opinion, but I do feel that OPI is over rated. One bottle is $18+ (in NZ) and the nail polish is no better than L’Oreal nail polishes. Yes the color selection is nice and the bottle fits nicely in the hand, but the polish lasts no longer that my L'oreal ones or even cheaper brands.
I do love the gold crackle effect polish though.
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!