I recently used the 3M kit to repair a big tear in a leather drivers seat, as well as some smaller tears.
Bottom line: the kit will repair the tears, thereby keeping them from getting worse, but it won't 'look like new'. It looks better than duct tape for sure, but it won't fool anyone into thinking its new leather. I repaired the leather on the drivers seat that gets worn from the driver getting in the car, and so far it has lasted 6 months, so it appears fairly durable.
That being said, I basically followed the directions. The way it works is you use the included fabric, and what appears to be very thick Elmer's Glue to fill the tear and level it off. Once dry, you cover it with colored rubber material that looks like thick paint. You basically vulcanize it using a hot metal spatula and a card that adds grain look.
I found that the iron method in the instructions did not apply enough heat, so I used a cigar lighter directly on the metal 'spatula' to get it hot, then rubbed it on the grain card that was pressing into the leather. It took a while to cure the colored material, which goes from sticky to smooth once it cures.
The critical bit is leveling with the 'glue'; it took me several attempts, waiting for it to dry between attempts.
Sorry I don't have photos because the car is not available right now.
