OPI had a captive market for mid-priced nail polish a few years ago but now there are other brands for the same price that perform better. OPI has a really good colour range that I will always appreciate and I wouldn't turn down an OPI nail polish if it was in a colour I really wanted. I do find they are prone to peeling off my nails after a few days, rather than having minor chips, which means I have to change my nail polish quite quickly.
OPI nail polish comes in quite generous bottles but I actually find I can't get through one before it turns gloopy!
Some of higher colours and finishes are great. I'm quite impatient with nails and tend to use quick-drying formulas, so I don't get to use my OPI as often as I'd like. The names are very cute and quirky though!