Well as an opinion as to our work in progress there are a lot of disadvantages to using Root Motion in a networked game as to predictability. The player movement component on the other hand is designed for network play but there is no reason not to have both if the RM animation is viewed as just another data set available based on the need in hand.
In our case the animations are authored as RM as it makes life easier for the animator not having to back key say a ladder climb but once imported the movement data is stripped off and and the player model bound to the PMC and the RM data used to correct the movement behavior as a imputed sample.
Root Motion is great as it is easy but the real question should be what would happen on a server with 100 players all using Root Motion?