WinRAR and similar will generally use the ramdisk to unpack data when you drag files out of the WinRAR window directly into Explorer or similar. If you simply right-click and click "extract to" then it will extract directly to that location.
I have used a Ramdisk for some time and found almost no problems using a Ramdisk with a size of 768MB with the Temp directories set to the ramdisk. This is on a machine that is rebooted daily. In my experience the actual daily use of the temporary directory is quite negligible.
The largest use of the temp directories happens with installers or as I mentioned when you browse an archive in WinRAR or similar and then drag a folder or item from that window to Explorer. The main reason for using the temp directory there seems to be that, not understanding the Rar format, the Explorer drag-and-drop function needs to be told "here is a file/folder for you" which needs that file/folder to be temporarily extracted. If you extract a file using built in functions "Extract to" or via the right click menu then the temporary directory should not be needed.
Due to the rather limited use of the Ramdisk (I saw a worst case of ~200MB used) I started using it more as a scratchpad for temporary work that I was happy to loose at the end of the day.
I don't think you are going to see any real performance benefit unless you put your browser caches there as well and set up other software to use it. In that case it it more important to think about their use of the ramdisk rather than Windows and Winrar.