My Reprap Prusa is still in it's early life stages. Amongst some of the problems I have had to solve one is the X end motor parts which are a little flimsy.
One problem that this created for me is that tightening the X carriage belt is difficult. The reason is that there is a fair amount of flex in the plastic part. I have read others who feel that the part has been stripped down a little too much and now is flimsy. Obviously you could create a new part with some more plastic in there to make it sturdier.
However this means getting your printer up and running just so that you can strip it down to add the improved part. I was looking for another way to strengthen the part. In my parts cupboard I had some aluminium angle bracket which I shaped and bonded into place.
I have created an SCAD file with the parts in it, though obviously this is to give a model to work from not to print from.
With this alteration the X motor end becomes rock solid and tensioning the X carriage belt becomes a lot easier. I can't comment on if it improves the print quality noticeably as I won't have before and after to compare but I would imagine it would help if you are having backlash problems on the X axis.