The button works nicely as a central symbol everyone (no matter their ritual predilections) can use. It's right combo of fun, scary and unique, and I think it has the potential to make Petrov Day... maybe not "mainstream" holiday, but slightly more mainstream than it might otherwise be.
The simplest, most fun/sound-byte-y elements of rituals (and, well, anything) will be the thing that spreads furthest and fastest. I can easily imagine a world where Petrov Day takes off, but most of the people celebrating it are not thinking concretely about X-Risk as a thing to worry about. (i.e. imagine how early Christians would feel if they saw modern Santa Clause)
(With the introduction of The Button, I now think this is is more likely than Petrov Day creating weird bad cult associations)
This isn't bad per se, but it's something to pay attention to when you're attempting to create cultural things.
Paired Button Technology is great for the original ceremony
One trait of Jim's ceremony is that it doesn't scale (up to 8 people as currently written, probably about 20 people if modified slightly). Since one failure mode is for too many people to try and come to one party, having a way for parties to split into smaller parties that feels *good* is important. Now, if your party gets too big you just say "alright let's have a paired party".
It also generally helps spread awareness of the day, incentivizing people to post on facebook/etc "Hey, we want to do a paired Petrov Day ceremony, anyone want to join us?"
It's fun, makes you feel like you're part of an overall larger movement, AND personally connected to particular other people.
More Deliberate Ceremony Around The Button Would Be Nice
This year the button was deliberately left open to interpretation/experimentation. I think it'd be good to formally work into the ritual (in NYC we ended up not formally introducing it until mid-ceremony, which ).
If that's the case, I think the Petrov Day Ceremony would benefit from a section that specifically introduces it, with some pomp and gravitas. Obvious places include "the beginning of the ceremony" and "after nuclear weapons are invented." (Or maybe "reveal" the button at the beginning, but do some "unlocking" action that makes it more dangerous)
[Also, this reminds me: I think Oppenheimer's "I am become Death" quote would be good to include, as would the followup "Now we are all sons of bitches.", and 'immediately after that' would work for unsealing the button."