Rated 5 out of 5 stars
This is awesome.I ran into some problems though (broken Awesomebar, back/forward functionality, and some other stuff too). But after I disabled it, restarted Firefox, and then re-enabled it it cleared itself out. Seems to be working fine now, not sure what that was about. Also not sure how I used Firefox without this!
EDIT: Turns out basically any tab behavior changing add-on (I tested several, notably Tab Utilities and Tab Mix Plus) created the issues. Tab Utilities is something I always use, mainly for the smart grouping. Pentadactyl seems to not have any of those features, although I'm still investigating. An example of what I mean by this would be that new tabs and searches with Pentadactyl always open in the last tab; then when I press "d' to close it I am sent to the tab directly to the left rather than the last tab I was on. I am then forced to use key combinations to get back to where I was, but if I close the tab normally (close button or middle mouse click) I am sent back to the correct, originating tab. This is confusing and seems to be counterproductive.
Furthermore, if I choose to use C-n or C-p to get back to where I was and am using the built in feature to not load every tab when I start Firefox every tab I pass through is loaded. Conversely, Tab Utilities allows me to use C-left/right to cycle tabs, but doesn't actually select the tab until I release Ctrl. This means that it is not displaying or loading the tabs I pass through until I actually stop and release the key, which is, to say the least, awesome. Pentadactyl may have features like this, I'm still wading through the copious amounts of documentation, but as far as tabbed browsing goes, the default settings are making me work much harder, even as compared to the default Firefox behavior (a simple C-w and I'm back where I started). But that's just my impression after a few days...perhaps I'm missing something?
EDIT: There is a plugin for the add-on that mostly restores the functionality. It allows to set where tabs open and the order tabs are selected upon close, which saves a ton of keystrokes. Seems like that one should be built in.