Hmm, replying to myself, to bump the thread. I just saw there was a very important option/action combo missing.
Option : comparing remote and local files by size. Identical size, or not.
Action : skip, resume or overwrite.
As things are, if we had to turn our PC in the middle of a HUGE series of uploads, and want to resume the day after, we can't re- drag and drop everything to the remote server, and simply tell the program "look at the file sizes, skip what's already complete, overwrite what's incomplete, and proceed with the rest".
That's very specific request that would not have widespread use. Moreover you can achieve this using synchronization.