Linux

Works great with HP Elitebooks G3–G4; honestly, worked great on any HP I've used. Might've worked on the Dells I'd used but they had other problems and didn't last very long so I don't remember.

But I've largely used older laptops so I'm not sure if the hardware, specifically, may have anything to do with it.

I've been using it pretty consistently for years, I achieve uptimes upwards of 60 days like this. The downside is that it takes kinda long to enter that state and there's a chance that it fails to enter it (though it doesn't crash, just goes to the screenlock), especially on my laptop - it refuses to go into hibernation unless I kill most webbrowser windows, especially stuff like YouTube.

And you do need a pretty large swap space; with those super long uptimes, even swap size = ram size isn't always enough, because sometimes the swap space is actually used as swap and not just as hibernation image storage.