Anyone ever use them?  Thoughts?

I have one on my SAR-3. It works well and allows much more leverage than the Krebs model.

I've had one on my SAR-1 and feel the same way as Thekatar. I had the Krebs safety awhile back and the SWIFT is sooo much better. Of course the AK purists will have a different opinion.

Of course the AK purists will have a different opinion.

That would be me.
With a little practice, the stock AK safety is very easy to work, and with your hand on the grip while you do it. You can also use your thumb depending on how your holding the rifle. My complaint with the add on safeties and mag releases is the protruding, sharp edges, that can hang up on things and inadvertently dump the mag or knock the safety off, not to mention, tear up your hands if your not careful. This doesnt really apply to the Krebs safety, since its more of a bump than something hanging out there. If you take the time to learn how to work the gun, I think you will find it's not all that difficult. It's really not the guns fault if you cant work it. If your into bolting on all sorts of gizmo's on your gun, kindly disregard all the above and carry on.

How does the safety work lefthanded?  Can you manipulate it with your thumb?

Quoted: How does the safety work lefthanded?  Can you manipulate it with your thumb?

Not unless you have monkey thumbs. It's really made for righties and it's activated with the trigger finger.

The bolt hold-open notch would be nice if you didn't want to break the rifle all the way down I suppose. But definetly not needed.

I may get one when I have some  money to burn.

Who sells the bolt hold open notch?

It's an option on the Blackjack lever. Mine has the notch - it works. I use it to keep the bolt held back when the range is cold.

Quoted: Good stuff, although I found that I can't use the bolt hold open notch with a Buffer Tech buffer installed.

Use a Dremel and make one yourself.

I thought about that. Would probably be very easy to do. Just might mess some extra blueing up.