I got the DIY edition of this a few months ago and have been using it continuously since then. Nice piece of hardware and I'm glad I bought it. Only big thing missing for me is user-modifiable firmware. Combine this thing with the Coreboot and neutralized Intel ME of Purism's products, and I would have no reason to use anything else. Currently this has a typical proprietary EFI firmware and no legacy BIOS support, which I wouldn't expect most people to care about but I find it a bit annoying.
I've also had some issues with the CPU temperature consistently pushing into the 90s when running big multicore workloads. Not sure why. Rather than look into applying new thermal paste or whatever, I just turned off Intel turbo boost, this is of course a performance hit but it keeps the whole thing very cool and improves battery life.
On an open UEFI solution, that is on our long term roadmap, and we're currently hiring for firmware positions to speed up kicking off this work. Edit: Also, our Embedded Controller firmware is open, though that is somewhat orthogonal to UEFI: https://github.com/FrameworkComputer/EmbeddedController