"oh no" that GTK2 is a sinking ship that everyone is fleeing from?
or do you mean "oh no" that Firefox is going to be at the center of yet another incendiary (and ultimately fruitless) debate.
Because I can agree that any one of those is a good reason to say "oh no".
So my knee-jerk reaction to say 'oh no' is just frustration that yet another app is going to start looking funny every time I update my system
https://igurublog.wordpress.com/2012/11/05/gnome-et-al-rotti...
Suppose I have a KDE based desktop which I gather uses qt as the widget library. Am I going to have another subset of libraries to run Firefox?
Currently I use a lot of hacks to get proper file selection dialogs in Firefox, as the GTK dialogs are just horrible to use.
The relevance of the "not again" is immediately apparent to people who've gone through a few GUI toolkits.