When you send files to someone, messenger shows how many kb is remaining. Is it possible to show also the transfer rate (kb/s)? And maybe how much time is left.

transfer rate could be possible I suppose, but it would only update when another packet got sent. How much time is left would require you to find out how much has been sent so far, at what speed and so on. It would be difficult to do and would not work on some wireless connections and some Vista installations (although my version of vista seems to work fine with xniff)

I don't think people are going to want to do this as it is too much work for a limited range of users.

However, I am in the process of making a script that adds all file transfers to a progress window in the same way as FireFox