I've seen speeds upto 40MBps. Use the streamer application and cystream firmware that come as part of SuiteUSB for the measurement.
The device would report its capability through descriptors, FX2LP would report USB2.0 support so if it is enumerated as full-speed you should see a pop-up with a message similar to device capable of operating at higher speeds you might want to switch the device to a high-speed capable port.
Thank you very much for the reply.
I have found out that the bottlenack was the embedded part - filling the endpoints. Removing the endpoints filling by the CPU and just submitting to USB (filled with junk) increased the throughput to 16MBytes/s which is quite good.