Seems ok for laymen installing only 12 gauge wire (they don't work with multiple wire sizes) with no tension (pulls out easier) carefully placed in an empty junction box, but not so much for other sizes of wire, and terrible in crowded boxes because the lever is easily popped open by other wires out of sight and then you may have a bare hot wire loose in your wall. That never happens with a properly installed wirenut.
I'll stick with wirenuts, they work great, are safer, won't let the wire pull out, and only sacrifice 3/4" of wire in the unlikely event they need replacing....and they're cheaper. Sticking with what works.

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Adding video to channels (Commercial) - requested by newtboy.

SHOW US YOUR NUTS!

Moving this video to bobknight33's personal queue. It failed to receive enough votes to get sifted up to the front page within 2 days.

Looks like the price difference between wire nuts and these is around 300%. 100 wire nuts for under $10, 100 wago connectors for around $30.

Hmm... wire nuts not reusable? Well, that's just BS. And you don't cut the wire when you're adding a new junction, you just turn the nut off and re-use it. Decades of electrical code would tend to disagree with pretty much every point made here.

These WAGO things are great. Haven't actually seen much else used here in Germany for many years. That in includes laymen and professionelle by the way

Saw this a while back on YouTube - plenty of professional electricians in the comments there who say they got so many callbacks on Wago, but never for wire-nut.

Personally I've had one fail (I didn't install it though) - my bathroom which was partially remodeled < 2 years prior, the light above the sink started flickering randomly. I checked each bulb, they were fine, so I opened up the switch box - and there were some of those Wago-style (a cheaper knock-off I suspect) that were quite loose when tugged. So I removed them, used wire-nuts, and it's been totally stable since.
The other benefit to wire-nuts is that twisting the copper wires around each other greatly increases the contacting surface area. (the surface of a wire is where the electrons/holes flow)