Sometimes, logging into game (ie, past character select, but not in game yet) will take as little as 2 seconds, even for Dalaran.
At other times, it can take 2-3 minutes for the log in process.
The average seems to be 30-45 seconds.

Once I'm in game, any loading is very quick.
The progress bar, for loading when taking a boat is fast enough that if I blink, I could easily miss it.