This is normal. Many people have complained about this before (including Fiesta owners), but they're just not used to dual clutch transmissions. This isn't a PowerShift exclusive issue either. The DSG system used in Volkswagens have the same issue. It's just how these transmissions work. They have a very notchy feel to them because they're technically automated manual transmissions.
What makes this different from regular automatics is the absence of the torque converter, which smooths out the shifting process. You're probably asking "well why the hell don't they have one?" Because torque converters are highly inefficient and sap a lot of power from the engine and reduce fuel economy considerably. The only solution would be to switch to a CVT or another traditional automatic car.
Sorry to put it so bluntly but that's just the reality of it. If it makes you any happier Ford is talking about development of an 8-speed transmission in the future (which is not dual clutch). Personally I would love to get my hands on a PowerShift car. Ford is probably the only manufacturer in America that is pioneering this wonderful technology for entry level cars (bonus points for using a maintenance-free dry system).