One of the common problems you find when FTPing files is that you run out of disk space! When you start an operation in the Finder, it preflights the operation to determine whether you have enough disk space beforehand, thereby preventing you from getting halfway through an action and then having it fail. FTP clients normally don't bother doing this and, as a result, you can sit and wait for 9 out of 10 megabytes to come down your modem and then have the transfer fail simply because you forgot to empty the trash!
An obvious way to address this would be to have the FTP client preflight the transfer and prevent you from starting an operation without enough disk space, in much the same way as the Finder does. This is an obvious, and a relatively good, solution, but Anarchie goes one better. When Anarchie detects that you don't have enough disk space for an operation, it changes the progress window to one like the one shown below:
In practice this solution is significantly better than a preflight with a terminal error because of the length of time taken for FTP operations. Normally FTP operations are slow and hence it makes sense to allow the operation to get under way and have the user utilise the transfer time to clean up the required disk space. Also Anarchie supports multiple, simultaneous FTP transfers and its common for there to be enough disk space to support each transfer individually but not in combination. Or sometimes another program (such as StuffIt Expander) consumes the disk space originally budgetted for the transfer. Either way, Anarchie's warning is very useful in practice.