i own a Cintiq 12wx and a Intuos3 A4wide
there is a couple of issues about this.

first of playing WoW with a cintiq is not desireable
at first it seems very cool, but you fast run into problems.
for example, when using it for mouse-look, its fucks up.
its 1:1 positioning system, makes it impossible to steer camera around.
second its very stressfull on your arms to work on a cintiq if your
arms dont rest on the table, this would happen when working with 5
cintiqs. third, you loose your focus from other screens when working
on one. with a mouse you can lean back and and have a glimpse look
on all screens, and switching focus doesnt mean you have to move
anything but your head a little bit, if at all.
To succesfully use cintiqs, would mean to have all screens very close
for easy interaction, which i think would stress the eyes very much.

however using a Wii-Remote is fun.... dont know why i brought it up.
alterative interaction i guess.

ill just advice you here, cintiqs, are stressfull for anything but drawing/working directly focused on the one screen.
extra monitors as in my case are for easy interaction with anything BUT drawing/working.
and definatly not fun for WoW, tried it, couldnt do it for more than like 30mins switching
back to mouse when i needed to look around.

IF should you nevertheless decide to buy x5 Cintiq21UX i would GLADLY
like to take them off your back, when you realize how much it doesnt work.

Calcifer

Edit: to answer you actual questions:
it functions just like a second monitor(reg. monitor) however underneath the coated screen
lies a tablet(much like tablet PC´s) which is mapped 1:1 to the screen on-top.

its super fast, just like a reg. mouse/monitor setup, same response time ect.
its just a touchscreen where only pen input works and not other material.
besides it has alot of uber functionality, 1024 pressure levels, tilt and rotation (input wise)
just to name a few.

really designed for painters and illustrators, not wow, sorry.