And better tooling. I'm unspeakably biased here, but I can't imagine doing kernel development without DTrace. (Actually, that's not true, because I did kernel

And better tooling. I'm unspeakably biased here, but I can't imagine doing kernel development without DTrace. (Actually, that's not true, because I did kernel development for many years without DTrace; it sucked.) So I would start with the BSDs or one of the illumos variants (e.g., OmniOS or SmartOS), and ask about small yet interesting open problems -- of which there are plenty...