Please post important consideration while selecting online broker here.

In my view,

1. How many shares you will be buying? This plays important creteria while selecting stock broker.
2. Are you Trading or investing?
3. Do you need prompt/quick support?
4. Trade execution time.
5. If Trader, Day trader or Swing Trader?
6, If you use margin, then interest rate on margin.

I started with Optionsxpress then changed to Interactivebrokers. Now considering switching my broker.

Earlier I was investing. Then changed to trading fundamental stocks.(I am not day trader but swing trader). Now most of the time investing in Pennystocks ($0.25 to $2.50)

For high volume interactivebrokers commision tends to be expensive compare to scotttrade etc.

Do your own DD and post your thoughts.