What does it usually take to download a movie (say 1.5 GB) from iTunes via cable (Comcast in my case)? I downloaded a 1.15 Gb movie and it took 30 minutes (which is only 0.63 Mbps).
I suspect you are mixing bits (b) and bytes (B)
A 1.5 GB movie is 12 Gb in size. If this were downloaded in 30 minutes ( 30x60=1800 sec) the download speed would be 6.67 Mb/sec (that's megabits/sec)
You went on to say "1.15 Gb movie" - that would only be a 143.75 MB movie and is much smaller than any of the full movies I have downloaded. For example, the 720HD third trailer of WALL*e runs 2 min 29 sec and is 101.7 MB. Your movie seems more likely to be 1.15 GB.
In any event, your speed is a lot better than I get with DSL on old copper telephone lines - you should be happy!