For me it has largely been okay, no real major issues. A bit of lag associated with textures loading, but that could also be latency as I am in Australia and I assume the servers are in the USA for the beta.
Only one thing that I find horrible. The lack of quick exit options from dunctions. Like the first story dungeon you come across there is a rope to get out. None of the other dungeons have anything of the sort.
One particular part is the story quest Light’s Resolve (Sorcerer). After killing the boss and running further to click on the thing on the ground and play the cutscenes, you are directed to run your way back to the begining of the dungeon to talk to Neyrelle, that is a large dungeon. After zoning through the end you have to run through the entire next floor to get to her.
Now that I have done it I know that I can just portal out and then get there faster, but the game depicts it as if she is at the beginning of the dungeon where she left you when following you.
You cannot zoom out to the main world map when in a dungeon, well not that I know of. I cant seem to find a way to do it. If you could zoom out or view the entire world map you can fast travel to the town near by and then just run there. Also you can see that the NPC has left the area where they are and moved.
Its nothing game breaking, but it is basically quality of life enhancements.