In my mind it's bit more concerning than the day to day of the cold war and closer to the last days of the Soviet Union in risk. Russia in its current form is in its end days. Do they go with a bang or a whimper?
This is where I am too. I'm thinking Putin is doing this as his last stand for his legacy. I expect that if he had done this swiftly he would have headed to the Poland border and maybe taken a right and headed up the Baltic (if he beat the Nato forces there).
I suspect he's surprised, if not stunned, by the difficulty that his forces are facing. So (while I would prefer he not risk it) I suspect his nukes won't work as expected either. I say that as someone who lives in the Boston suburbs, which I suspect is a high priority target for his subs.
Most importantly, perhaps, is that if it is WW3, it's going to be the world against Russia. Iran may try to help if they feel an obligation; I don't think China will because they're smart enough to see it's a lot cause.
I do not think there's a way to assign probability to this situation.
If we assume Putin is mad, there's no reason why he wouldn't throw a nuke. Due to downside being inevitable, WW3 is a logical outcome. Otherwise we are just letting him throw nukes.
We have to hope their system is not setup such that Putin can unilaterally launch. Is there not some military officer or guard in the way who could decide to save the world?
Personally I like to think that if I had the means then I would be in a well stocked bunker deep underground. Possibly until the Mars colony is ready.
But I am kind of poor so I have an excuse for ignoring it. I do think that most people are just in denial. The same way most Ukrainians were about the possibility of a war.
No one successfully coping is going to be clicking on a 'WW3' thread in HN's 'new' queue and telling you about how they're successfully coping.