No, I mean the kernel,specificly a linux or BSD kernel. Yes and update would be a pain, but I really only update my kernel every 4-5 months anyways.
As for features, the netwoking stack comes to mind. It's basicly it's own little OS running under your operating system.
As for the log dump, isn't that what is bricking some of those Samsung laptops? And this is far from the only bug that shows up (some will check the string name of the payload before running it and refuse to boot anything that isn't windows or redhat) . Runtime services aren't supposed to call boot services after boot, but this doesn't always happen and this can make it hard to work with. There is a huge amount of code and specification, much of it not well understood by by more than two or three people, but not a lot of tests or formal verification to make. At least if you run UEFI/tianocore on top of coreboot, you're running and open source version that can be updated at any time without worrying about weather your hardware init will keep working.
I have one computer, my laptop which is UEFI, (2.2 i think) the rest are some sort of traditional BIOS.(award, phoenix, whatever). Oh, and I love the kernel EFI kernel stub, the fact that you can flip straight into the kernel within two seconds of turning on the power is awesome. Having it be finished loading in two second would be even awesomer.