Seriously. I am moving, after a long absence, back into the markets. Paper traded FOREX for some time now using MetaTrader - and HATE it.
Platforms seem to be few and far. Taking out the data feed issue, my current plan is:
For stocks:
* Go with ameritrade, as tehy have an API (yeah). I can get quotes from them, as w ell as handle the trade side. Maybe I will do some yahoo integration to get the EOD data.
* For Futures and Forex:
Zen-Wire starts looking good, plus one of their integrated brokers.
Platform - GOOD question

I had a look so far at MetaTrader- sucks (sorry), the UI is non-sensical and I regularly blow by making the wrong trade. Closing a pyramid of positions is hard work, thanks to no "exit all of that instrument" method.
* NinjaTrader - still trying to decide whether I should laugh. Definitely a good framework to run a system, tbut I still need a way to "integrate" that with my development environment (Visual Studio), but they do C# based systems. Have some nice order entry mechanism that I REALLY like. You can prepare a order strategy (stop loss, trailing profit stop etc.), in a window (one per instrument), then hit "ENTER" and be done. But their charting is not good - definitely a focus on system / semi automation.
* Right Edge - well. C# again (I love it), but.... I rather prefer MY development environment. I earned my living with C# for 10 years now. I have all the tools. And I do not want a "mock up semi good IDE" where I can not integrate my toolset.
I seriously plan of doing some combined thing myself, but use ninja for now.