My long term review of the Shimano GRX RD-RX400 rear derailleur with an 11 sp 11-42 cassette using Ultegra 6800 11 speed shifters: It works great! After a few long gravel/ MTB and road rides, it is shifting great! Much better than the 11 sp Ultegra RD-6800 with Wolf Tooth Road Link. I would say that it is definitely worth the $63.00
https://www.jensonusa.com/Shimano-GR...ear-Derailleur