If you do this, ensure the system has more RAM then you ever actually use. Allocating an in-RAM disk leaves less RAM for system & apps, causing the system to page/swap earlier than it otherwise would have, which is a huge performance hit.
I find a more cost-effective performance boost is to use an SSD big enough for the boot, system, app installs, and temp files. Then use conventional "spinning rust" discs for all data. This also cleanly separates system/binary from data, facilitating data preservation (backups & restore). And facilitates OS upgrades, as you can nuke the entire system/SSD drive without losing any data. It also gives some level of virus/malware protection, as none of your data resides on the main system drive, and your Windows-allocated default user/data folders are all empty.
Of course, that's when I have to use Windows. Better yet, don't use Windows at all!