This is the first feature I immediately felt compelled to change. Tabs are visually represented with a spacial order, and there is nothing to indicate order of access. If I can see the tab I want is two to the left, and I can't remember how many "tabs ago" I viewed it, pressing CTRL+shift+TAB twice is thoughtlessly easy and conceptually simple.
You can remap this functionality, but this particular key combo doesn't seem to work.
By default it was on ctrl+3/4, and I don't think it's a wise choice as ctrl+number is good for either selecting first 10 tabs (chrome, ff), or for opening a speed dial entry (Opera=<12). I would actually like both of these functions, perhaps on alt+number and ctrl+number.
I prefer CTRL+TAB and CTRL+shift+TAB because they can be used with one hand moving the hand only slightly from its natural resting position. It also remains essentially identical on almost any keyboard. Neither of these are true for CTRL+PGUP and CTRL+PGDN.
Ctrl-Tab/Ctrl-Shift-Tab (along with other tab management keys like Ctrl-T and Ctrl-W) are nice because you can hit them using only the left hand, with the right hand remaining on the mouse.
I don't remember X tabs back either, but you can't go back and forth between two tabs unless you place them next to each other and then use two separate shortcuts. That's a deal-breaker for me.
