Out of curiosity I did the switch towards new-tabs.js and used your css from the wiki. 

Indeed the tab-bar does not flicker anymore.

The numbered tabs are pretty user-friendly, especially when used together with the tip "Switch to buffers
1-10 using number keys 1 through 0" from http://www.conkeror.org/Tips. (I made C-(1 to 0) switch to
buffers 11 to 20, as I usually open more than 10 buffers, but wouldn't propose something like that as a
default binding.)

Although I still miss the favicon, I don't intend to switch back.