Well, no, feedback shows it is totally unreliable crap. While it works here on my Odroid N2+ booting from USB and SD card, it does not work booting from eMMC. Other users, especially all HC4 replies I have, booting hangs in initramfs, not being able to find the rootfs, even that kernel and obviously initramfs was loaded from there already.
Also I totally fail to understand the reason why Hardkernel developed and uses it, instead of using just plain U-Boot. petitboot is basically a wrapper of U-Boot (at least its implemented like that) with some configuration CUI. But it lacks basic syntax of U-Boot, even the syntax that is supported by the ancient U-Boot version they wrap. So it limits the possibilities of (the underlying) U-Boot, adds complexity and points of failures, and at least with mainline kernel a lot of points of failures do indeed apply for many users, while for some its like this, for other like that, just a pain in the ass.
I do actually more and more regret wasting time to try adding reliable support for it, because to me it seems it never intended to support any other kernel than the highly customised and ancient vendor Linux 4.9 of Hardkernel. And that is what we feel now on all ends.
The only reason I did all this was that petitboot comes preinstalled on Odroid N2 and HC4 SPIs and that it is not so trivial for inexperienced users to flash proper mainline U-Boot onto that SPI flash. I wanted to allow booting DietPi from USB without the need of any additional flashing steps and first boot from X, then flash y, then boot from z annoyance. But it seems to just not work like I was hoping for.