I know I can ctrl-pgup/down in Firefox (it's the best alternative to alt-tab afaict) but on one of my laptops it's incredibly impractical (pgup/down is way up the top right), and on the other pgup/down is in a practical, but very different, location to tab so it's "disjointed" in my mind (ie "do I want to go mru? ctrl-tab; do I want to go ltr/rtl? alt-tab" they're still in the same area, and hence it seem logical/simple to switch between those options often, whilst pgup/down seems very different?)

(And then meta-tab is also hanging out there, being simple and ready for an alternative context switch (mostly browser <-> terminal).)