I'm assuming you have memory to burn and don't care about power failures. You'll need to consider if your files' sizes could eventually scale past the point where they won't fit on your ramfs since it may be a pain to rectify this when it actually happens (e.g. you may have to add more ram, fix code, or move it to a disk fs). Obviously, handling this with a disk fs is easier since you can give it a large amount of space ahead of time.

Also, sometimes you'll see little/no significant benefit over using a fast local disk filesystem. Ram filesystems still have to simulate creates/reads/writes/unlinks/etc and, depending on your access pattern, disk filesystem caching can make huge differences.