I was very pleasantly surprised with performance on Vivec (PC-EU).
Spent a couple of hours there between about 4 and 7pm GMT, campaign was locked for all factions, had no crashes, a bit of lag but nothing particularly bad, 1 or 2 loading screens mid-riding but those lasted only a second or so. Joined a large group, took some keeps, did all of the kill quests and generally enjoyed it a lot.
I've seen people complaining of poor performance also on Vivec (PC-EU), so I wonder what happened there. In any case my own experience was very positive, to my own surprise.