Popping the MRX shifter open to get to the cable resulted in breaking the shifter, for me. It had been left outdoors for some of its life and it was brittle.

I was interested to see the new shifter for the left is not a mirror of the right but instead basically a right with different markings and many (like eleven or twelve, not three) detents. So instead of shifting backward from the other as shifters always have, they both shift the same direction; and the massive quantity of detents effectively gives you FD trim. I'd call those both improvements. That doesn't mean the quality is any better, though.