On ChromeOS (and maybe other os) Google added a feature, that lets you switch the open tab by swiping on a touchpad witch 3 fingers. This feels increadably intuitive and i would love to see a firefox equivilant implementation.
Other Touchpad Gestures are already supported in the current nightly build so, im guessing this is possible as well.
Technicly this can be done witch 3ed party programs (at least on linux), by mapping 3 finger swipe to crtl (+ shift ) + tab, but that can lead to weired unwhanted zooming an other problems. Also a firefox native solution would support some animations.