Just wanted to quickly provide some feedback and see if others have had the similar experiences.
Server: Thelanis
Was generally farming Night Revels for keys last evening for close to 4 hours (7-11 EST).
The Good part: Whereas there had been lag spikes fairly often over the weekend that would freeze all action for several seconds at a time, I don't recall that happening at all last night. At worst, there were a few 'blinks' where action would hang for a second or less, but nothing debilitating in that regard.
The bad part: There was one instance of a serious lock-up. Not sure if this effected everyone, but my game client locked up and kicked me out of the game. A re-log required several minutes as the 'loading game data' screen was delayed considerably.
At the time this happened I had just exited the 'Newest Ringleader' quest... others were there on that rock as well, plus there's a guild that likes to hang out together on the rock bridge next door. I noted the largest spawn of enemies that I'd ever seen occur on that rock bridge (somewhere between 20 and 30 based on the overhead red bars)... and suddenly all movement stopped. A couple of minutes later came the crash.
I can't say for certain, of course, that the proximity of so many players and so many spawns led to the crash, but it seemed circumstantial enough to go ahead and make this post to explain the observation.
Of note: I don't believe that event participation was quite as high as it had been over the weekend. Probably to be expected, but that might also temper a proper evaluation of 'the good part' above.