I bought two ADF4151 eval boards and am in the process of designing a board with the '4151 PLL chip and a proprietary VCO chip on it. The concern I have is with the USB to SPI interface. While it's not a big deal to copy the hardware (CY7C68013 USB microcontroller, 24LC64 EEPROM, ADP3334 regulator, and all the passives), my recent experience with a similar PLL+VCO chip and porting its USB to SPI interface from the evb to my own board was that it was far from trivial. It took me and my team quite some time to gather the drivers and such and get it all to work smoothly.
Maybe it's easier with the CY7C68013 since it's a microcontroller vs. the FTDI FT2232D USB to serial interface chip that was on my previous board? I could use some help on this since my board needs to be ready before the VCO chip comes back from the foundry in early June.