Got about 10 hours in today spread across two servers, Tarro Blood and Kaas City. Those two (both PvE) were as stable as they could get. No issues at all and was playing on a laptop and a wireless connection, so no mega vid card or high end NIC and there was no visible lag or stuttering and once ingame video settings were changed (initial default was low) textures looked much better than I saw in beta. As always though, your mileage may vary.