I've seen bad things happen with those, they really are not to good for carrying high loads.

Gotta agree with that! Same thing with those self-locking terminals on outlets.

Those wirenuts pictured would work really good in 4-lamp troffers, you connect both ballasts on the hot with ONE wirenut, same thing for neutral!

How do these 'work'?

They have a springy copper piece that locks in wire by holding against a copper plate when a wire is inserted. Here's how one looks disassembled.

I personally only use them to extend fluorescent ballast wires and to connect HID caps (some HID ballast kits have those connectors for the cap). All building wire I use good old wirenuts.

Yeah, I wouldn't use them for any high-load circuits, but for typical household applications like lighting, they are fine.

They are rated for 20 amps, I like these well enough but I mostly use wire nuts, mostly because they are much cheaper.

UGH! Not those POS of wirenuts! Good for wiring fluorescent fixtures. Not so great with house wiring where you can put heavy loads like the vacuum cleaner.

I haven't had one of these fail, and some have been pushed easily to 15 amps for long periods of time... People really don't like change, at least you don't insist on soldering and taping wires together...

Yeah there's a lot of debate over these online. Some people love them, others hate them with a passion.

As a licensed Electrician, I would agree they are ok for lights but not for junction box wiring. I'm good with change but certian stuff just isn't as trust worthy IMO. I have seen many times back when I actually did residential wiring, seen the stabacks on receptacles burn up on serice calls from high loads.

Also, I noticed the box isn't grounded.

Good eyes. There should be a green screw under that somewhat clean gull nest.

They are rated/certified for it, therefore they are acceptable. From my understanding these are different from the back stab receptacles, which I don't use at all. I will agree that wire nuts at the moment are better though, and much cheaper. And yeah, you should ground that box!

Yeah, I still gotta do that.

What does this power anyways?

The 4 T8 fixtures in my garage.

Ah, I figured that out after I commented.

@ Niall, Remember this one thing, It's your License on the line when you wire homes so Electricians will use whatever makes them comfortable, IMO I would not use these for JBOX wiring thats all.

Well I guess for me I never really trusted push in connections for high current connections, especially since I've seen some push in outlets with toasty neutrals.

I personally never use those push-in connectors. i use wirenuts just becuase I have so many and I can use those with stranded wire. Push-in connectors are only supposed to be used for solid wires. As for grounding this, if the fixture is grounded, wouldn't this be grounded too because the conduit is metal?

It's not conduit, it's armoured cable. As a matter of fact the metal jacket of armoured cable was used as a grounding path for years, however it is now not allowed. So yes the box may be grounded but I wouldn't take the chance.