“Hello world” takes on new dimensions in this context.

Pff... and I can debug a stupid bug from 0.00001 miles for the 3rd day.

I'm a little surprised by their approach. I mean, it did work, it is cool, and it is the most important thing. Still I can't stop thinking that I wouldn't sleep before I wrote an assembler and a disassembler. Judging by the presentation they had no assembler and disassembler for several months and just lived with that.

asm/disasm can help to find typos in listings, they can help to find xrefs or even to do some static analysis to check for mistake classes they knew they could make. It wouldn't replace any of the manual work they've done, but still it can add some confidence on top of it. Maybe they wouldn't end with priors 50/50 for the success, but with something like 90/10.

Strange. Do I underestimate the complexity of writing an asm and disasm pair?

Puts things into perspective. I often wonder how so many people survive without a UI debugger because cmdline debugging seems too clunky.