Generally if I care enough to style/mod an app it’s because I’m using it a lot and its stock UI isn’t doing the trick.
Sometimes it can also drive me to switch to a different app, like with Firefox. FF used to be my secondary browser, but Zen (a Firefox fork) aligns with my needs and preferences better and doesn’t require userChrome mods and addons that are likely to break after some random update some day, so I switched.
Thunderbird would benefit from its own Zen-like fork in my opinion. Its UI has always felt clunky and awkward, and the “new” design just shifts around the awkwardness.
As someone who thinks browser UI peaked in 2008, Zen just feels like Firefox UI designers on ritalin. Had to about:config hack it to show the KDE system titlebar. This software is not for me.
Since a couple of the machines I use regularly have small screens (12-13”), hiding the standard titlebar and collapsing browser UI elements into the titlebar area were among the userChrome mods I had been applying to Firefox, so that particular bit of UI design in Zen is desirable for me.
On desk-bound machines hooked to 27” displays, this isn’t really necessary, but the UI being built around vertical tabs as the standard (as opposed to most browsers, where vertical tabs are a tacked-on afterthought if they’re even supported without addons) is still a relevant selling point.
Sometimes it can also drive me to switch to a different app, like with Firefox. FF used to be my secondary browser, but Zen (a Firefox fork) aligns with my needs and preferences better and doesn’t require userChrome mods and addons that are likely to break after some random update some day, so I switched.
Thunderbird would benefit from its own Zen-like fork in my opinion. Its UI has always felt clunky and awkward, and the “new” design just shifts around the awkwardness.