No, I use FTDI boards (3-4 variants) all day long at "Uno Speed" 115200 baud. Same speed as the 8/16u2.
Upload this sketch and open your serial monitor at 9600 baud:
http://arduino.cc/playground/Main/ShowInfo
Type "i" in the input box and copy out the information and paste it in the forum. I want to verify some settings.