I recently replaced two Chamberlain chain drive openers with new Genie screw drive models. On one of Chamberlains the up-limit switch wouldn't always work, and the carrier would slam into the stop bolt and jam tight. I emailed Chamberlain and they said it could be a number of things causing it, but most likely the limit switch would need to be replaced. Instead, I replaced both openers with the new Genies. No more problems, and the Genies have been fantastic so far.
By the way, Chamberlain assembles their openers in Mexico, and Genie assembles in the USA. I'm not saying Mexico = bad (my truck was built there), but if given the choice I'd prefer my money go to some American workers.
- Mike