I am, to my knowledge, the only multiboxer on my server (Trollbane - Horde - US).

You will get a lot of people stopping, and "wtf"ing, but to be honest, I've not had a lot of negativity. A few "get a life"ish comments, but I just ignore it. Most of the conversations I've had have either been positive, or just neutral questions (want to know how it works).