I've ordered about a dozen things from Outpost, across four orders.
When it's in stock, they ship either the day of the order, if it's early enough in the day, or the next day.
For the stuff that's been pre-ordered, it tended to show up within a week of "release" to the public. Standard ground shipping (which is what I get from them) gets me what I ordered in 3-5 days.
I guess they weren't taking any chances with Halo 2, since if I waited 2+ weeks and didn't get any real discount on it, then I'd be a little irked, yes.