Works as advertised. Used it twice on some worn stihl chains. First time took 15 minutes. Second time took about 5 minutes. Other reviewers said to squeeze in small bites and adjust. They were spot on. Works great for my stihl 029 chains.

Had to use grinder to remove most of rivet before taking the chain apart.

This chain breaker probably works great on lighter chains. In the case of a chainsaw chain, it had trouble doing the job on its own. I finally used a small grinder to remove the rivet heads on one side and then used the tool to push the rivets out. I purchased the following two items to reassemble the chain: Oregon P23837 Tie Strap - 25 Pack and Oregon P23910 Preset Tie Strap - 25 Pack.

Very nice tool handy so i can keep it with in the feild for easy repairs

I have tried one and have observations.

It uses the same principles as an Oregon bench breaker and spinner but on a Vise-Grip scale.

Have good vision and good lighting so you can see what you're doing. Practice on a junk piece of chain until you get it figured out. The "preset" tie strap has to end up between the anvils. May have to rearrange chain on top of both anvils to keep tie strap level and stable between the anvils. Should have a measurement such as 5/16" anvil spacing for a 3/8" chain so you know about how far to set anvils apart. Understand the basic construction of a saw chain. Don't put a cutter between the anvils instead of a tie strap. Center the punch on a rivet and dent it and go on to the next rivet and dent it and then tighten the handle screw some and repeat. If you do it right, eventually you will get a satisfying pop. Try to keep the "presets" straight and reusable. Then you round the "preset" and then you spin the rivet. I didn't spin the rivets much for fear of overdoing it.

The Granberg Break-N-Mend seems to work for getting more life out of stretched chains, but if you're going to make new chain loops out of rolls, you might as well have a bench breaker and a bench spinner and maybe use new presets.

It seems that the most likely part to give you trouble on the Granberg Break-N-Mend and on any chain breaker for that matter is the punch. A replacement punch can be found by Googling. It might cost more than a little bitty punch should after paying shipping, but it seems to be pretty much the only part subject to wear or misuse.

10/2/2014 edit: There seems to be pretty much no reasonable homemade substitute for a genuine Granberg punch.
I checked out what a replacement punch would cost.
Bailey's: $4.99 plus $7.95 by USPS or $9.99 by UPS.
Granberg International: $5.80 plus $14.99 by UPS.
However, they say: "Granberg will always ship at the lowest possible rate. Please note that prices listed are for items that cannot be shipped by mail. Small parts and Ripping chain typically ship for less than six US dollars."
So, if you get them on the phone you might get shipping cheaper than $14.99. They also offer Anvil Assembly, Spinner Handle and Spinner Head as spare parts.