I think a lot depends on which iPhone you're looking to get. For example, I went to my local Sprint store to get on the wait list (Tuesday 9/25) for a Black and White 64GB (bought a $50 gift card for each phone to get on the lists, which can be used to buy the phones when they came in).
I was #2 and #3 on the list for 64GB, however the list for 16GB was like 50-something people and the 32GB had 20 or so on the wait list. Long story short, I got a call the next morning that my phones came in. It was less than 20 hours from the time I placed the order until I was called to pick them up.