I received the 2 Arms today that I ordered, could not wait to put them up so I would have my 2 30" Displays Wall Mounted. I started to put the first one up, I pre-drilled the holes into the studs. Using the scr-ews provided with the mounting arm. I tightened the scr-ews by hand into the wall, and one of the scr-ews snapped in half. So after I go to Lowes and get some scre-ws that are not made of some kind of che-ap & we-ak metal to cut costs of production; I will have to end up remounting higher or lower than originally planned, due to the fact I have the threaded end of the scr-ews stuck in my wall now. So do not Use the provided scr-ews, I would not want to have this happen to anyone else. Costing well over $100 for each one of the mounts, I would expect they could provide some nice heavy-duty scr-ews to mount with. I don't even want to think what would happen if I actually got to the point where my 30" Cinema HD's were mounted on them and then the scr-ews broke, that would have been quite costly.
Moving my 24" imac is a grinding process that is jerky and hardly one touch. I have tried to loosen the allen wrench nuts to get the right combination of tight enough to hold it up and loose enough to move freely and have not found a happy medium. Within 2 months it wont hold the iMac upright, any adjustment loosens it beyond usability.