I use R for almost everything related to modelling and testing. It infuriates many 'pure' programmers but it really can't be beaten when it comes to exercising your creativity and testing out new ideas. Anyone who says python is superior in this regard is simply ignorant of one or both of these languages. As soon as the markets open, however, responsibility is turned over to the native apis. IBrokers is ok for basic tasks and is certainly a much better effort than most people would be capable of but it is nevertheless buggy, poorly documented and unreliable. If you are depending on it to save you during live trading when things get hairy you will get badly burned.