I have been trading personally for 9 years, and have quite a few friends that trade as well, so I have some decent feedback on all the firms you mentioned. You really need to decide what type of trader you are when deciding firms. Interactive Brokers is really for someone who doesnt need a robust platform and just needs execution, the service really isnt there. MB is a decent firm with decent service, the platform is ok, the commissions are decent, but they still clear trades through Penson, and I have seen some stocks that I couldnt short - since Penson has alot of Daytrading firms they clear, the good shorts seem to be missing. Terra Nova I found to be a diamond in the rough firm, my friends have found very competitive rates , though they do not publish them. Since they are self-clearing and have a decent short list from Merrill and with the choice of platforms and good service, I feel that they have the most complete solution. Looking at some deals they are doing on the Investment Banking division that they recently started. So there you have it, in summary, all the firms you mentioned are decent, so it really depends on what your looking for.