It might be because I have a 5 year old subscription and that other rules apply, but I pay the $60,00 and backup everything from .txt, .php, .cpp, many gigs of .avi etc. (I would never get to 500gb otherwise)
No trouble from my ISP. Being from the Netherlands, I obviously have a 100/100 fiber connection. So it really isn't that much.
I have all my data in a separate partition, reaching 1.5 TB. With say 2 MBPS upload speed, it seems it would take about three months for the first upload.
Also, did you face any issues with data limits from your ISP for the first upload?