Recently I got to know that VIM has identified this problem quite some time back and has a solution in store. You can open a remote file over SCP, where in VIM would bring down that file to the local system and store in some temp location. You edit that temp file, with VIM running on your own machine. So do not have to wait for keystrokes to be processed by the remote machine. When you write the file, VIM updates the remote file using SCP.
[Note]: If the file is read only, w! will not work. The user account used for SCP must have write permisson for the file you are editing. Otherwise, obviously, remote write fails and VIM will promptly report it.
Look at this page for the syntax and more details.
This would be straight forward on a linux box as both vim and scp come packed with the OS and they are in the shell execution path and everything is set up by default. Things need some extra work on Windows.
First obvious thing is to install VIM. Then you would need a SCP program. And once again PuTTy comes to rescure. They have a PSCP.exe, which makes you feel at home even on Windows. Get it here.
To improve this a little more you can rename the PSCP.exe to scp.exe and place it in "C:\Windows\System32\" so that it will be picked up from everywhere at the command prompt. Also note that you can use your PuTTy saved sessions directly with PSCP.
Happy remote VIMming. :-)