That's actually why I haven't gotten any ML Transformers yet...Optimus had some issues with the die-cast and plastic that occurred often enough to wind up in a warning on the wiki, and Bumblebee and Cliffjumper's ankles are known breakages waiting to happen. I'm very iffy on the cost-to-fragility ratio.
I find that the wiki is sometimes overly cautious. The wiki states OP's thigh swivels are "extraordinarily tight." This is not true. I didn't even know the toy had thigh swivels until I read that, so I tried them out, and they're totally fine. Needed to "crack" the joint, but after that, it's good. As for plastic-on-metal, time will tell, but no problems so far. The hip joints are totally fine.
It's good to take care with toys, especially these expensive collector imports. But I haven't had any trouble with ML Optimus, Cliffjumper, or Bumblebee.