I've tried a few different colours from OPI and I think their selection is amazing but I don't think the quality throughout the whole range is overly consistent.
Some colours I've tried are awesome and have amazing lasting power, but some end up peeling completely off my nails by the second day of wear.
An awesome positive to OPI that i've found is that none of them have stained my nails, which is amazing. Almost all nail polishes apart from OPI will stain my nails and I hate that, so avoiding stained nails is a big thing for me (especially when i'm so bad at remembering to use a base coat).
I would totally recommend people trying these out, it's worth it for the colours and selection, just not always the lasting power - but everybody's different and may have amazing results with each one they try :)
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.
Tips: Go to opi.com and try the "Try-It-On Studio" (sidebar on the right)- it is awesome to try and figure out colors for your nail length and skin tone.