Why does the kernel matter so much to you?
In terms of userland tools, OS X has pretty good compatibility with an average Linux distro (yes there are obvious differences between *BSD and GNU implementations of various tools).
Personally I think you should give Apple a(nother) look in terms of a productive workstation machine, even if that's paired with/using services from/developing systems for Linux-based servers.
Compare yours to "Apple's admirable open source program is genuine and legit. If you've unfairly dismissed them in the past, give them a second look."