I actually was alliance for about a year, switched to horde for two years, and I've now been alliance again for over a year. I don't know if I will return, I might in Cataclysm but who knows
edit - I agree with MidgetMage. You should reroll entirely instead of switching. It tends to be very overwhelming, and I like to just reroll myself to get to know people and such so your not a stranger, and you know some people before hitting lv 80 or 85 :P