I have to toss in on the rollout issues... DoF appeared smooth, then again, I didn't buy it until about 2 weeks after it's release as I was re-levelling a toon and wasn't really in the mood to spend more $$ (long drama with SOE that I lost but still feel I got a raw deal on, but what's done is done)
KoS was a NIGHTMARE. Server crashes game lag and I didn't even have the expansion yet. It was pretty rough, but seemed to smooth out after the first couple of days. Working in IT, I know that you can't prepare for EVERYTHING, so some tweaking is necessary...
BUT. Faydwer... SMOOTH. I can't help but think it had something to do with the fact that by release date most of the content was already downloaded to our systems. I'm sure there were SOME issues, but honestly, nothing sticks out.
Here's hoping RoK will be the same!
What we have to consider is this; no matter how much testing you do, each server is not identical, so there's bound to be variables no one thought of.