I encountered a strange issue.
The latest 32 bit version of SmartFTP, running on Windows Home Server (I believe it's Windows server 2003 code base), when downloading via a fast internet (Verizon FiOS), can write to the local C: drive with a stable 2.5MBytes/sec speed for hours.
However, when the download destination is set to a 64 bit Windows 7's network share \\server\share, the speed drops significantly to only 200 - 300 KBytes/sec.
The puzzling fact is, from this Windows Home Server, with xyz downloading the same file to the same network share, the speed is stable at 2.5MBytes/sec.
This made me think it's probably a SmartFTP issue.
In my case, when the download destination is a UNC name, SmartFTP would not abort an ongoing transfer (Abort has no effect) in the queue; stop the queue would not stop the ongoing transfers (even though the stop button is disabled and the start button is enabled); shutting down SmartFTP (click the X button) would not terminate the SmartFTP process (The UI does disappear, but I had to kill the process from Task Manager).
All those three problems (along with the significant slowness) won't be there if the download destination is a local drive.