There is a sticky post at the top of the msg list that you'll find all kinds of info. Plus a search of the forum will bring up more posts than you'll have time to read.
Overall you'll find that the majority of people love their interchangeables and the majority love the Knitpicks Options or Harmonies best. I have Denise Interchangeables and Options. I don't even use my Denise needles much anymore, I love the Options!