So, it's not just me, lol.
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They actually use two separate LEDs and detectors. In addition to the standard infrared LED and detector that other photoelectric detectors use, they also use a blue LED and blue light detector. Nest calls split-spectrum detection. The infrared detector detects large particles associated with slow smouldering fires. Because blue light is not as easy to diffract as red light, the blue detector detects the smaller particles associated with fast burning fires.
As this split-spectrum technology is relatively new, Google/Nest published a white paper on how it functions, available here. (warning - link is a PDF).
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And they tell you if they are about to sound in cases where your 30+ year old kids are smoking in the guest bedroom even though you've told the multiple times there's no smoking in the house (ask me how I know).
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Same here. They're pricey but I've never had a false alarm in the 5 years I've owned them. Their auto-self test feature is excellent, they have a number of great family friendly features, and the announce which room smoke is detected in.
As for the other brands; I've been woken from a deep sleep more than once while single First Alert or Kidde smoke decides to chirp at 3 in the morning only to find it's impossible to tell which one is chirping.
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The early morning false alarm a couple days ago, after the spider decided to make a second traipse across the sensor, I went down to the basement and threw the breaker. It's totally hardwired, except for the CO's , which will need replacement soon.
Your hardwired smokes donât have backup batteries?
Nope
Are they pretty old or do you just not put batteries in?
Pretty old.
I just looked. Ours are First Alert. I don't know who owns what, as far as brands.
The First Alert page seem to only have battery backup for their hardwired now.
How does that work: in a power outage, do they all still alarm, or just the one(s) that's affected?
With Nest, the answer is yes. Cannot speak to how the other brands work without AC power.
I think this one has both wired and wireless interconnect, with a backup battery. The wireless interconnect will keep working during a power failure.
Some newer hardwired models from First Alert and Kidde come with 10-year sealed batteries, which a great for avoiding the (always middle of the night) low-battery chirp until the device itself is at end of life anyway.
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I was actually thinking that with the battery backup to a hardwired system, you could just throw the breaker and the offending detector would still be alarming.
Yes, if false alarms are an issue, then flipping the breaker wouldnât stop the false alarm.
But all hardwired smoke detectors come with backup batteries these days so that the home is still protected in a power outage.
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So, is it your experience that ALL of the hardwired detectors will alarm during a power outage, even if they are not in smoke?
My house doesnât have hardwired detectors, so I canât speak from experience. But I wouldnât assume all models from all manufacturers behave that way, no.
With Nest, yes, and they will identify which Protect is sending out the alarm. The voice feature of the Nest Protects makes them >100 WAF in my house. (And I like them too.) 
If interconnected, all detectors will sound, that's the point of interconnected.
If not interconnected, then only the single alarm goes off.
I don't know if hard-wired and interconnected are always found together.
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Theyâre not. At least they didnât use to be.
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I love my nest protects and I too have them integrated into my HomeKit. I use virtual switches to perform automations if smoke or co2 is detected along with pushover notifications. We have a dog that is scared shitless though when the voice from the sky starts talking. Lol.
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I don't even bother with pushover, the nest app works fine for that. But I use ecolink firefighters to integrate them into Hubitat.
