Thanks for thus posting. Just installed mine today, note about not undoing cable gland screw saved me lot of potential work.
I found taping bit string to Intuvia cable before removing worked well, then tape string to Purion cable and pulled it through.
Had one issue with Purion would always turn on initially, left it for 10minutes and worked fine.
My first impressions are good, no longer distracted by big centre display, miss time display but not important. One of big drivers behind change was switching handlebars, have Jones bar plus original MTB. Lot easier to switch than Intuvia, plus it made switching stems a not easy.
Like big walk button on bottom, should be easier to use than old one.
The bell next to display should give it a bit of protection.