I thought it would be a nice feature in our application to reboot the device after a firmware update and not have to cycle power on the device. I found that the reset was not working. I found 2 things. They may already have been fixed/documented.
1. in DFUDeviceReset() in tidfu.cpp (of the tidfu.dll), comment out or remove the code to make the device idle. If you don't, the command will not be processed in the bootloader.
2. In the bootloader, in UpdaterUSB() in bl_usb.c, make sure to put EALLOW-EDIS around the setting of the watchdog registers.