Uplink usually has less to do with your client than your uplink bandwidth. It all depends on what the bottleneck is.
Lin, what's your uplink bandwidth, what's your latency to the dreamhost servers, and how many hops do you have to your server?
I'll test something out at work because my uplink from home is only 5 mbs or 625 KB/s and that's only the theoretical. I don't think I've ever come close because it's just DOCSIS 2.0 cable and you know the problems with that. I'll test it out from work but I hear that our uplink at work is limited both intentionally and unintentionally by our proxy and firewall. I'm also hampered by my 85 ms latency to the west coast, where the dreamhost servers are.
BTW, I have heard that there is a big difference in performance between certain ftp clients on the Mac. I know it sounds crazy, but there it is.
BTW, WinSCP is free so you can try it out for yourself. I will only be able to give you SFTP bandwidth results because I refuse to use FTP for security reasons.
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