I've been an Ameritrade client since before Ameritrade (when I was a Datek online client). I also have accounts at Schwab and Fidelity.
It's all what you are used to, and I use the Ameritrade tools far more frequently than either Schwab or Fidelity.
Ameritrades thinkorswim application has amazing capabilities, with complexity to match. There is also a Java based app called Trade Architect, and you can also just trade online using their web interface.
Ameritrade also provides gain/loss tracking using Gainskeeper, which I prefer over the Schwab and Fidelity equivalent.
Having said this, changing over is always difficult and frustrating. That was even true way back when Datek was bought by Ameritrade (for both their client base AND their technology platform), and I know it took me time to get used to the Ameritrade platform.