The more recent versions of Dataram (e.g., 3.5.130R24) have been causing me some stability problems. I get strange blue screens (not BSODs, because there is no white lettering and no reboots). It seems from the entries that my registry cleaner removed after I uninstalled Dataram that they have changed the program recently. Maybe they will get the bugs worked out at some point, but they don't have a nice forum like this to raise the issues either.
I have been trialing Primo Ramdisk on two different PCs for the past week or two, with no problems. I like how it compacts files, which helps me out in my application, and also how fast it loads and unloads the image. I will be buying it if all continues to go well.