I'm a huge OPI (and to a lesser extent, Essie) fan. I think OPI and Essie both have great colors and last-ability, but I think the thicker OPI brush is so much easier to paint nails.
I have a whole system when I do my nails (which is pretty often):
-Cuticle Remover (Sally Hansen Instant Cuticle Remover)
-Push back cuticles with cuticle stick and wash hands
-First coat of OPI Nail Envy
-Two coats of OPI or Essie polish
-Top coat of Seche Vite dry fast top coat... the MOST. AMAZING. TOP COAT. EVER. Dries quickly and with a super shiny finish. Seriously, you can do almost anything within 20 minutes of applying this top coat without smudging your nails. Amazing!
Current OPI color obsessions:
OPI I Brake for Manicures
OPI Ski Teal We Drop
OPI Honk if You Love OPI
OPI French Quarter for Your Thoughts (Super similar to Essie's Chinchilly)