S3 multipart uploads
It's a great tool you have here, I love it, but the upload speeds are magnitudes lower than my upload bandwidth limit. Uploading a large backup file (tens of GBs) is taking 8–10 hours.
p.s. I wanted to donate again (as I did a long while back but it must have been on another account as it does not show), but PayPal has shat itself for me, and they've no support – it'd be great if there was another method for payment.