Our transfer rate averages from 1GB to about 10GB per hour per account.
However, in many cases, it is very difficult to predict how long a given transfer will take. Depending on the number of directories, the number of files, the size of those files, and the source/destination, it can sometimes take longer than expected to move your data.
What may be surprising is how large of an impact factors other than the size of the data you are syncing can have. For example, it is not uncommon for there to be 1-5 second of overhead per file being copied (target service needs to catalog this file, index it, verify it, etc.). If you are trying to move 200,000 files, this would be 200,000 – 1,000,000 seconds, or up to 11 days of overhead alone!
Furthermore, some cloud apps and cloud storage providers have throttling limits (for example, Microsoft OneDrive), which can influence your transfer speed.
For Dropbox, the performance may start to decline when you store above 300,000 files as described here: https://www.dropbox.com/en/help/39.
We are working hard—both with our partners and on our technology—to make sure your data is replicated as quickly as possible, and to give you as much visibility into your transfer as possible. We are working on some very exciting state-of-the-art algorithms, so expect to see some big improvements in both transfer speed and feedback soon!