Further to my post on my initial experience with Netflix, my first DVD arrived on Thursday - that's four days not one.
In the meantime I reported it missing. They have quite a neat facility on the site for doing this and it seems as long as you don't report an unusually high number of DVD's missing, it's factored into their business model.
Interestingly, the replacement DVD was shipped on Thursday and arrived today, which taking account the fact that the Post Office was closed yesterday for Veterans Day, meets their one business day target.
It's only a sample size of two with a mean of 2.5 days. I suspect as I collect more data it will eventually settle around 1.1 or 1.2 i.e. 80 or 90% will arrive in one day with the occasional one taking longer. It probably was just bad luck that it was my first DVD that took the slow boat/train/plane/truck or whatever.
From this experience I've decided that their one DVD at a time plan is a waste of money. I've upgraded to the two DVDs at a time plan so I can always have one to watch while the other is in transit.