i just started using opi and i love it. i used to not do my nails very often once i got rid of my acrylics because everything would chip on me (my job is very manual labour intensive) and end up looking crappy after my first day at work with them done.
i bought opi base coat, top coat and sweetheart and midnight in moscow nail polishes a couple weeks ago to try them out after reading about opi online. i didn't expect much, but i'm super impressed. i prepped my nails with a basic manicure and then used the base coat followed by sweetheart finished with the top coat and it lasted me an entire week without chipping. probably could have lasted longer, but i bought italian love affair after seeing a swatch here and i wanted to try that on instead.
i'm really happy with how opaque the colours are, you only have to do one (maybe two) coats to get the colour to show up on your nails the way it does in the bottle, which is a big deal for me. it applies very evenly, too. i don't have the steadiest hand in the world, so i love a nail polish that doesn't streak. i use pure acetone to clean up my little mistakes around the edges and cuticles, and it looks like they've been done professionally.