It took me longer to install the full SD3 than to download it. I have a 400/40 connection, with regular d/l speeds running over 300. If a file took 45 minutes to download, it would take 60 or more to install. If the drive contains only installers, you've still got hours to go.
But it's totally worth it!
EDIT: I'm trying to remember, but I think the distribution files downloaded from Amazon S3, not directly from Toontrack. I was served as fast as my connection could handle.