I believe that "last seen completed" is not that easy to implement since it would require a modification of the protocols (not likely) or some sort of feedback-server whereto all completed downloads must be reported and this would require a lot of data-capacity and network traffic.
The trick with the incomplete-folder is possible - but not usable for the basic user. Since it is an easy thing to implement in raza it would be nice to have such a feature.
Consider columns "Last data received", "Last data sent", "Overall ratio" and "Estimated completion" where "overall ratio" would be the bytes pr. second ratio since the transfer was started and the "estimated completion" would be a calculation of time spend divided by data received multiplied with remaining data (converted to a timestamp - a programmer should understand that... sort of

)
The columns must not nescessary be in the transfer list - they could also be in the transfer properties dialog.