I just got an IB account and plan to dump my Datek/Ameritrade account, especially if they will not pro rate commissions. I "heard" that customer service at IB is terrible, though. But I love the fast fills and low commissions. As far as I remember, the commission charge is 1 cent per share up to 500 shares and then 1/2 cent per share (.05) for all above 500.