Dave Nanian, proprietor of Shirt Pocket, which makes the backup utility SuperDuper! has a lot to say about the upcoming APFS file system in macOS High Sierra:
The bad news is I’m not confident enough to say we’re going to release our APFS support day-and-date.
I know this kind of hedging is disappointing. But it’s important to note that Apple still hasn’t released any documentation on the “proper” way to create a bootable APFS volume. An example of what they have in mind was released for the very first time when the High Sierra developer release came out a few months ago, but that’s it. We basically have to make an educated guess about what they want.
Dave suggests caution in upgrading to High Sierra, especially for those using SSDs, since they will be automatically converted to the new file system. Keep an eye out and see what other people’s experiences are before taking the leap.