Man, the game really runs terribly when windowed, I've noticed. If I look down while gliding over the city when the game is windowed, I drop to about 25fps.
If I look down fullscreen, I remain at 60.
It's just so annoying, since the game more or less ceases function half the time if it ever loses focus when fullscreen (not to mention that it minimizes, which is never good for an MMO), and I like to switch out to read websites on my other monitor while waiting for queues and such.
And since the game MUST be run via the launcher, none of my programs that can force it into a "windowed maximized" mode (like most MMOs use) work.