I keep seeing people complaining about lag... the first response is ALWAYS 'Your GFX card sucks' or some variation. I've seen people say that about a GTX460 1GB GFX card..... that's ridiculous. There is Server Side Lag going on because it is release of the new FF MMO.
Here's why I say this:
My computer - Running FFXIV on medium graphics (on Configuration, Shadows and all that turned ON)
MacBook Pro 13" 2010
CPU: Intel Core 2 Duo 2.4GHz
RAM: 4GB DDR3
GFX: nvidia GeForce 330m 256MB
I am running FFXIV and I'm experiencing absolutely no lag whatsoever. I also have an HP Elite i7-860 (2.8GHz), 8GB RAM, GTX460 2GB tower sitting at home and it runs the game EXACTLY the same as my Mac in terms of responsiveness.
So, to everyone scrambling for a new GFX card... wait for a week or so. Unless you have an old Pentium computer or something, chances are you GFX card is -fine- to run the game. Unless you're picky and want to see every water drop on every scale of Leviathan... I see 90% of the water drops on 90% of the scales of Leviathan and people thought Mac's wouldn't be able to run it at all... look where I'm sitting.
To those that say "Well, I have -no- lag, it can't be server side!". Check what server you're on. Some servers may be more full, some may be more laggy, it honestly depends, so saying you have -no- lag is not a justifiable answer.
Bottom Line: It's server side lag... wait for the buzz to settle down, everything will run fine.