I have a verizon FiOS 100mb/s service. Speetest indicates I'm getting a little bit more than that. Despite this, it just took me a little bit more than 14 hours to download a 5.43GB movie.
However, if I choose to stream this movie directly from iTunes to my Apple TV, no problem. It starts within a few seconds and plays smoothly.
I target iTunes downloads to a Western Digital MyBook Live NAS, and I'm suspicious that this may be the problem, at least in my case. The NAS is connected via ethernet to my router, which my iMac is also directly connected to via ethernet. It should be very quick, but it isn't.
WD issued an update for Mavericks compatibility just before Mavericks was released, which I installed. I'm also now running on Mavericks.
Are others who are experiencing this slow download problem downloading directly to their Macs, or to external storage like me?