I had my LV's take a full 24 hours. They said if it takes LONGER than that, you can file with them for some fee refund...whatever.
One thing I noticed is that if you use Auctiva (which is free), the Auctiva scrolling header shows all your items immediately. So, if someone is looking at another of your items, they can actually see the "invisible" listings as soon as you list them, rather than waiting for hours and hours.
It's not perfect since they don't show up in search, but it's interesting that someone could potentially do a "Buy It Now" on something from the Auctiva scrollbar before it ever shows up in the search!
(I'm thinking this is a great way to get some good deals from my favorite sellers before most people see them!)