Multiboxing is extremely common on my server. And our top rated raider ( he also happens to be my best friend ) has two shammies, so we don't get too many whines about it. The only response I get is: "OMG cool, twins!" People love seeing my baby mage and shammy running around. I even tagged a mob someone was going after on accident, ( can't see very much when you have two wows! ) I apologized quickly after I noticed him, and helped him take down another mob as repayment. He didn't say one word against me, but launched a conversation asking me if multiboxing is hard.

People on my server have a healthy respect and curiosity about multiboxing, especially when i tell them that i am all manual. I have even gotten instance groups for the twins, and i let them know that i am both the mage and the shaman, and am new to the whole thing, and they have no issues with taking it slow.

One plus to multiboxing: if someone is trashing your friends, you reply to them, they ignore you, pop over to thing 2 and lol as they get angrier.