The UART-firmware uses the USB-connection on the nucleo's ST-link, and it's limited by the bitrate of the ST-link's USB-UART connection.
The latest firmware is written for the STM32F405-board from this project:
and it uses the USB-controller in full speed mode (12Mbps) to communicate directly with the PC.
I've used ST's USB-driver (SPL-version), and the MCU presents itself as a virtual com port, so the CLI and GUI for UART can be used without modification for the firmware.
Clocks, PWMs and communication are all working. I'm going drinking, so tests with a TCD1304 in place will have to wait.
oh right and the firmware can be found in the files section.