I'm sure that most of you, guys who are using Windows VISTA already hate the "smart feature" that is "Calculating time remaining to copy files", which takes more time than the actual copy itself. Well, may be under some circumstances it may speed-up networked copy of files, but in the common scenario it just slows down the whole process.
Thanks to this post, I've found the way to remove the irritating feature and go normal again.
The culprit seems to be the "Remote Differential Compression" feature, which is introduced in VISTA for the first time. To turn it off go in Control Panel / Programs and features / Turn on or turn off Windows features and uncheck "Remote Differential Compression".
Another feature that might slow the network traffic is the TCP/IP "Receive Window Auto-Tuning", which can be turned off via elevated command prompt:
netsh interface tcp set global rss=disabled
netsh interface tcp set global autotuninglevel=disabled
After these changes you might want to reboot the system and look for improvements.