@martin: Tracked for 8 years with no apparent work on it :(
Great! Good to know, this would be perfect for me as well. I have the same speed problem.
Would it be possible to add support for parallel transmission of a single file? For example I notice that I can make 3 different files transfer at 9MB/s (3MB/s) but a single file will only transfer at 3MB/s. Would it be possible to have WinSCP break the file up and send it in 3 different connects?