If you're at all worried about it (and just not wanting to deal with crap is, I think, a valid worry), and you want to PvE, allow me to suggest Lightbringer Horde! Lightbringer is not a multiboxer-heavy server, but it is a very multiboxer-friendly one. The worst I've ever gotten is one dude who wanted to inform me -- very politely, if incorrectly -- that multiboxing was against the ToS. I told him that Blizzard has explicitly cleared multiboxing as OK, and he said he didn't know that but was happy to hear it. That's my horror story. Lightbringer Horde is Pleasantville for multiboxers.