Another issue is the treatment of Java apps. They have tightened up when and how they get fired up. By default they will not run Java apps that did not come from the App Store. Even if you change that to accept Java from anywhere it's hit or miss and often miss.
My broker has a non-App Store Java app that downloads, verifies, and starts another Java app. Well, part two of that fails most of the time. That's a major PITA. That app lets me see the Level-2 market orders, i.e. those orders that are the same or lower then the current "bid" and same or higher price as the current "asked" along with number of shares. So you can see the "depth" of the market for a stock. Given that I always use limit orders, it helps me to see all this in setting my prices.
Of course running Java apps from anywhere has its own exposures.