I am using uploading files using the "Send To" context menu shortcut entry in Windows Explorer which can be created by the WinSCP installer.
A while ago, the upload progress window was visible in the task bar, so you could easily read its progress and switch to the window if necessary. This is no longer the case, so it's hard to track progress, and when using the "minimize" button in this window, it becomes completely invisible.
Sometimes, the dialog shortly shows up in the task bare when reaching 100%.
In case it's relevant, I'm using Win7 x64 with the "classic" (Win2k) theme, not Aero.