I find it can really vary. I've had movies load in as little as a few minutes and as much as being left over-night. And, I think that variance depends as much on your ISP's network performance as it does on Apple's. Once, I ordered a movie over the AppleTV that took several hours to download, yet while it was downloading from Apple I was able to download it in about 30 minutes via bittorrent. Clearly, at that time, the slowness was on Apple's side.