Unikernels are unfit for production
Bryan may certainly be right (I neither know him nor much about unikernels), but some parts of his argument seem incredibly weak.  The primary reason to implement functionality in the
  operating system kernel is for performance...

OK, this seems like a promising start.  Proponents say that unikernels offer better performance, and presumably he's going to demonstrate that in practice they have not yet managed to do so, and offer evidence that indicates they never will.  But it’s not worth dwelling on performance too much; let’s 
  just say that the performance arguments to be made in favor 
  of unikernels have some well-grounded counter-arguments and 
  move on.

"Let's just say"?  You start by saying the that the "primary reason" for unikernels is performance, and finish the same paragraph with "it’s not worth dwelling on performance"?  And this is because there are "well-grounded counter-arguments" that they cannot perform well?No, either they are faster, or they are not.  If someone has benchmarks showing they are faster, then I don't care about your counter-argument, because it must be wrong.  If you believe there are no benchmarks showing unikernels to be faster, then make a falsifiable claim rather than claiming we should "move on".Are they faster?  I don't know, but there are papers out there with titles like "A Performance Evaluation of Unikernels" with conclusions like "OSv significantly exceeded the performance of Linux in every category" and "[Mirage OS's] DNS server was significantly higher than both Linux and OSv".  http://media.taricorp.net/performance-evaluation-unikernels....I would find the argument against unikernels to be more convincing if it addressed the benchmarks that do exist (even if they are flawed) rather than claiming that there is no need for benchmarks because theory precludes positive results.Edit:  I don't mean to be too harsh here.  I'm bothered by the style of argument, but the article can still valuable even if just as expert opinion.  Writing is hard, finding flaws is easy, and having an article to focus the discussion is better than not having an article at all.