In case you didn't know, Zul'Gurub will be gone in 4.0.3. For those bad with numbers, that is not the upcoming patch, it's the one after that.
Why should you go there? Well, if you want to get the exalted title at one point, Zul'Gurub rep is pretty easy to get. You can get those bijous and various other turn in items and, even better, you can go in, clear the trash, go out, reset, etc. In any case, it wouldn't be a bad reputation to get to exalted.
Also, you might get one of the mounts.
Also, since other people will probably be doing this, those bijous and coins might actually sell well to.
In any case, if you are mostly trolling in the trade chat, go to Zul'Gurub, it's worth it.