I read comments like this every now and again, most often from novices transitioning from Rockwell's and other more affordable options, unfortunately however they are untrue in that they are formed by a cursory aesthetic appraisal of the Mergress razor rather than from a practical consideration and understanding.
The Mergres modification is not just the addition of a metallic knob, the modifications entail adding extra weight to the razor (12-14g) and tightening up the tolerances within the existing Progress manufacture itself, known problems with the razor such as blade alignment, replacement of the C clip and adjustment mechanism are rectified by Eric and are the product of a considerable amount of time and experience being considered in his work and applied to the razor. I see them on the BST's for around $80 USD for a short handled model, and around $95 USD for the XL - I would argue that this price point alone makes them a preferential option over a $300.00 razor with a questionable performance and release history.
I have read widely that there are considerable problems with the Rex, multiple revisions, recalls and customer dissatisfaction with the product and it's important that people are aware of the issues prior to them making a decision to drop $300.00. I found your opinions on the razor interesting and indeed instructive from a certain perspective, largely they confirmed what I had read and your experience lends further weight to those already out there.
It's a pass for me, product issues aside (rectified or otherwise) for the level of build and final product it's just too much of a stretch given the final result.