I'd throw in my vote for switching sides as well for a nice fresh twist on things. I was a PvE raider (2box mage/priest) for years horde side... took 18 months off and rolled my new multibox team over on alliance and the combo of new questlines, cities that I didn't really know my way around in etc etc was enough to really bump up the engagement factor for me.

of course I only made it to 50 or so and realized that I preferred the horde races aesthetically... but by then I was good and hooked on the 5 boxing thing so re-rolling (again) wasn't a bid deal