I tried it yesterday and was surprised how it gave pretty much exactly the FTP I expected. I've not done a Ramp Test before but it is easier than the 2 x 8min or 1 x 20min protocol. It is only really the last 2-3 minutes that hurt and is intended to make testing less daunting and more accurate. There is a TrainerRoad Beta Group which you can join if you want to test Beta features on TR.
My FTP when I started the Sweet Spot Base II a few weeks ago was 251. I had expected to be at 255 now and hoped for 260. The Ramp Test put me at 258, so pretty much bang on, and the way it is done means that it is harder to decide what your FTP should be and then try and do the 8 or 20 min intervals to achieve it.