Works perfectly, despite being like 8 or 9 years old now. I've read dozens upon dozens of books on it, it still works like new, still syncs well, has multi-month-long battery life, is lightweight enough to keep in a bag at all times. Works perfectly with OverDrive for eLibrary stuff as well.
My only complaint is that it uses the old micro USB cables to charge (it's the only thing I use regularly that doesn't work with USB-C).
The new Kobo's look nice (and now support color, and bluetooth audio, and such). But I wouldn't actually use any of that, my old one still works just like new, and it feels silly to buy a whole new e-reader just for a minor USB-C charging convenience.
I personally really value the "sideload" mode on the Kobo where I have no internet connection and can drop my files onto it via USB without any work-arounds. That's enough for me to keep using the Kobo.
That said, the Kindle Paperwhite's display is incredible and the store is pretty good (you risk losing your book "license" on all platforms), plus the extra small bit of screen size on the Paperwhite is just the perfect size IMO.
But the Kobo is the one I use most. I connect it to the internet like twice a year to get an update and then turn it back off. It's absolutely perfect at showing me text of files, which is all I need.