For some people it is, for some its not. I'd say if you really like doing a lot of longer exposure night shots in urban areas from a tripod into direct sources of light, you should DEFINITELY stay away from it. If not, its a matter of how perfect you need your cameras to be. I've had a couple of orbs show up in a couple of thousand photos - in one it was pretty bad, in the other hardly noticeable. That's well within my tolerances for imperfection. But some people are really bothered by even the possibility of orbs and they certainly CAN happen under certain circumstances. I'm keeping mine for the foreseeable future and if I ever do sell it, it won't be because of orbs...
-Ray