SOG:
I dont have any and Ive only receintly handled one. Dont know which model it was but I wasnt that impressed. A friend pulled his out to do some work on a washing machine. When I used it, I found the tools easily folded back while using them. Needs a lock or higher tenssion to hold them.

LeatherMans:
I sent my first Wave (old style) back under warranty. The jaws went loose after a couple of months. It had a lot of play in them, and you couldnt cut much with the wire cutter because the jaws would move apart and just kink the wire. Fixed under warranty. They wore out fast too. My 2nd Wave (old style) has lasted a bit longer but is starting to show signs of ware.
I havent found that any of my Leathermans will hold an edge on the blade very well, so I am continually resharpening them.
My SuperTool has been fine, but is showing signs of ware. That lives in the car tool box now.
My Mini Tool doesnt get much use, so that has been fine.
My Crunch hasnt had any problems either.

Another problem I did have with the first Wave is that sometimes a bit of dirt or something would cause a bit of friction and the knife blade would sometimes open while using the pliers. I have been lucky and not cut myself, but it is quite dangerous if you dont watch for it. The second Wave didnt have that prob. Because Leatherman use a funny shaped tool to hold the pliers, I cant adjust the tension on the pivot point for the blade, so I just make sure its kept clean.