I finally beat Black Mesa. The Gonarch can throw hands eggsacks. Once out of that I breezed through the rest of Xen. The second half basically keeps your health, armor, and gluon gun constantly recharged. It reminds me of the final section of Half-Life 2 where you become death. I'm glad the final boss doesn't do that teleportation nonsense.
As a final note, I want to let the AI programmer for the headcrabs that my hatred comes from a deep place of respect. Not only do they do a significant fraction of damage, but are quick to re-engage. More than a few times I busted out the shotgun so I couldn't miss.