I think the Aleph objects X ends are wonderful. That said I had to tweak a few things to make them work well for me.
I opted not to go with their version 1.1 as a basis because the original seems more than sturdy enough already, and is easier to make work with the larger #6 nuts and uses less plastic.
nuts and bolts.scad values for M3 is changed to fit #6 nuts.
The clamp part has been altered to grip the smooth rod better - as originally posted, it just slid on my smooth rod. Without strong clamping, the Z rods get pulled on when the belt gets tightened.
The motor part had part of the bend impinging on the larger hex hole of the #6 nut - fixed.
Top of the nut space in the clamp part is now a conventional bridge layer rather than a cone shape, which just caused a huge mess for me when printed.
NOTE: After using these for a while, I found that this design for X ends tends to telegraph every tiny wobble of the Z threaded rod into the print. I think it would be a good idea to redesign this to hold the nut loosely and have a millimeter or so play in the shaft as well, to let the threaded rod and nut float a bit and hold tight to the smooth rod instead. Personally I've switched to thing 25047 as my preferred X end now.