Ul'dah seems to have become the most populated city on every server.
In addition to the points Catapult mentioned, Ul'dah had the best leves in terms of SP rewards: Nophica's Wells and Broken Water in particular. Because of the player traffic, the Ul'dah markets also became the best place to buy and sell goods.
...
Saronia has a pretty strong Japanese player population so it tends to be quite active during the evenings here. I think the Japanese players on Saronia are also quite talkative in /say because there are a lot of cross-LS friendships.
NA prime time is much more quiet.
