From what I know, Xfast RAM is a RAM disk on steroid. So it's aimed at anyone who needs a RAM disk, 32bit or 64bit OS. The extra features of this utility (as per version 2.09) are:
1- Can indeed map and make available RAM beyond the 4GB limitation of a 32bit OS, but confined to the RAM disk only. So if you have a 32bit OS with 8GB of RAM, the OS will only "see" 4GB, but Xfast RAM can create a 4GB RAM disk with the unused RAM left.
2- Can emulate a "ready boost" partition mapped to the RAM disk to accelerate your magnetic hard disk drive, just like an SSD would do. If you already have an SSD boot drive or a small SSD acting as a ready boost drive, this option is useless to you.
3- Option to automatically move your memory pagefile to the RAM disk. 1 click in the Xfast RAM interface, reboot and you are done. No messing around with windows config.
4- Option to move temp and cache of Internet explorer and Firefox to the RAM disk. Again, 1 click in Xfast RAM interface, reboot and you are done. No messing with windows config.
5- Option to move both (and independently if you like) the system temporary files and/or the user temporary files to the RAM disk. 1 click in the ... you know the drill.
6- Option to backup the RAM disk when you shut off the PC to keep the content intact and ready to use at next boot.
You can assign any free drive letter you want to the RAM disk. You can choose the size of the RAM disk. Apparently, it can support RAM disk size of 8GB for 64bit OS and 32GB for 32bit OS. I benchmarked the RAM disk with Diskmark and got 9800MB/s sequential read with a i5-2500K OC to 4.7Ghz and 8Gb of RAM @ 1866 10-9-9-28 1T (ASRock Extrem4 GEN3). Got very similar result from another Ram disk utility. Xfast RAM is the most versatile RAM disk utility I've ever tried.
NOTE: Beside the obvious gain in speed (huge gain with Photoshop apparently), this utility is highly recommend to SSD users to limit / reduce write operations that will degrade your SSD.
NOTE2: With 8GB of RAM in my PC, I've created a 1GB RAM disk and it's more than enough for the vast majority of scenarios. I've only encountered limitation with archiving utilities such as Winrar and 7zip. Both app have the option to specify the temp folder of your choice if you need to create archives larger than the maximum capacity of your RAM disk.