I like the fact that it makes them more accessable, but I'm hesitating even changing the caps on mine. Why must I be so nostalgic?!
Well, they didn't make that many expresses and if you want people who've never seen an express to know "This is what 399.99 would buy you in 1990" keeping the screen authentic, with dead pixels and all is part of that. I'm a big believer in not modifying rare hardware besides for repair, so cap changes are fine, but things like AV mods or stuff that change the functionality of the original hardware I'm not such a big fan of, if it's rare hardware.
On common systems I have no problem with people doing this, since I have no doubt 20 years from now there will original common systems that function as they did stock. On rarer systems like US Duo's, Expresses and Neo-Geo's I have reservations as these systems just aren't that common.
With that said, it's up to the owner as to what they want to do with it, obviously for practical purposes the replacement screen is a significant functionality upgrade. It really comes down to if you're keeping it original for nostalgia and collecting purposes, or you just want something to play TG games on the go.