Well, I tinkered with the X-mark some more, and here are my thoughts...
Off the rack, it is better than the standard trigger, but that's where the superiority ends IMO.
Without taking the whole trigger apart, the only thing that's adjustable is the pull weight. If you adjust it lower than a certain point (which feels like at least 4 lbs to me) the sear will not stay engaged when you close the bolt.
The problem is that as the overtravel and sear engagement are not adjustable (the screws are epoxied or something... no way you're getting them to turn without completely disassembling the trigger and using a solvent...) you have to rely on the trigger spring to hold the trigger in place far enough back to let the sear engage.
With too much overtravel, on a light setting the trigger will flop loosely, and that's why the sear won't catch.
So, you can't adjust the overtravel to keep the trigger aligned with the sear, and you can't adjust the sear engagement inward.
I'm also still having the same problem with inconsistent trigger pulls. The only solution I've found is to set and then release the safety before each shot. I believe that works as the safety mechanism and overtravel limit are one in the same.
Overall, even a clumsy nail bender like me can get a better result from the standard trigger in just a few minutes of adjustment.
YMMV, but I'll be replacing mine. I'm a big fan of Timney's, so I'll likely go that route.