patsystem is the software. IB use its own software. Patsystem is available at several brokers.
I have tried a simulated mode of patsystems. It seems complete. But you know what ? despite all the comments about IB's interface [not all justified imho] I like IB's direct approach better.
However, I must say that I understand more IB's interface and ways since I trade almost only futures. IB does this well. I had more complaints when I was trading stocks. Anyway, there are many threads with pros and cons on the subject in this forum.
if you want to trade futures I can't see how you would not love IB. if you trade NYSE I think you gonna like it too. If you trade Nasdaq, pros and cons are more balanced.
neo