I have a very large collection of OPI nail polish. Compared to $2 shop nail polishes these are amazing. Personally my nails have trouble getting nail polish to stick and not chip but normally I'm pretty fussy and change my nail polish regularly. There are sooo many colours, its so exciting to choose which ones I want to get. Personally I don't think they are worth the $20+ from farmers etc but you get them cheap at makeup bucket sales, ebay or I use candygirl.co.nz and they have a large range for around $18 and they are super fast and nice :)
The nail polish does not thicken which is a massive plus (except the shatter) and normally requires two coats. The colours sometimes fade to a lighter colour but with a top coat there is no problem at all.
I LOVE OPI Nail Lacquer, it is one of the most high quality nail polishes on the market and comes in the most spectacular range of colours- literally every colour for every occasion. Like many high quality items, the price can be a bit of a bank breaker, however if you can stock up at one of the massive beauty sales it's all good! Price aside, my main issue with OPI is the drying time, it seems to take forever! And even when you think it's dry, it's not as I always seem to end up with the criss-cross marks from materials etc. If you have the time to sit around and wait for it to dry, then OPI is my number 1 go-to.
Tips: Like any nail polish/lacquer, a base and top coat will make it last longer :)