I spent the better part of two evenings diagnosing an issue where Grbl would either stop responding or run off to a random location when issuing some rapid commands.  After finally swallowing my pride and posting a bug report to the forum, it took about 10 minutes for someone to point out my mistake.  My configuration was using a 41 khz step frequency which is above the Grbl max of 30 khz.  Since this Arduino was used for development and wasn't connected to my CNC, there was no visual indication that the step rate was way too high.  Ah well, problem solved.

Once that issue was worked out I resolved a few inefficiencies in the communication state management, added the ability to show verbose output on the console page, and changed the Settings page to have an explicit save button instead of auto-saving when a change is made.  I also performed basic 4-axis tests with the grbl-Mega-5x fork with promising results.