I'm hoping to spark a discussion on this topic. I've used multicharts, IB TWS, anvil, sterling, LASER, Tradestation, tradelink, ninjatrader (on IB), and to a lesser extent thinkorswim. For the record, I thought Anvil was by far the most superior user interface to all the other trading applications, but I am no longer in a position to use Anvil. I used Anvil in 2005, though, so things have changed. I am mostly an automated trader, but the user interface is important to me because it can either make or break how I develop new ideas. Feel free to post screenshots as to why you think some feature of your favorite platform is so critical.