I still remember in SWG the issues it brought as players were able to keep characters knocked down.
Even I don't understand how designers keep implementing the root feature in MMOs.
I have been playing WAR lately and well, in PvP you really feel like someone's taking away your keyboard.
I ask this question: where's the fun? It's like beating a dead horse.
It would work in slow paced combat but now 90% of the time the root = death.
Unless the root has a huge draw back on its user I don't see it as an interesting mechanism.
Maybe the solution is to keep it for PVE only.