I strongly recommend IB. I trade a portfolio of stocks and issue more smaller trades. IB's commission structure is unbeatable. Their TWS software is also very stable: I've had very few problems in the past. Nothing compared to the hassles I had with CyberTrader. If you trade few stocks in larger volume ( >1000 share trades each time), I'd also recommend CyberX2. CyberX2 worked well for me, but the higher commissions were enough to drive me away.