I would like to throw my two cents into this well of debate as well, if there are no objections.
Kirin is indeed
highly powerful. It's lightning incarnate, and it can be aimed. It
is, however, only TRULY useful in finishing off an opponent which is incapacitated, yet extremely hard to kill (examples... Kakuzu/almost any Uzumaki/Orochimaru/Snake Cloak Kabuto/someone who can regenerate quickly/a Kage/Danzou/Gai or Lee with Gates, probably 5 or more open would cause them to be very hard to off). Coupled with perhaps a
hard beating
beforehand after which the opponent would be hard-pressed to move quickly, or Ino's Mind-Transfer, or the Nara clan's Kagemane... this
theoretically incomplete Kirin which we have
seen already may belong in that category that comes as the final strike against an
immobilized opponent, even despite it's literal lightning speed.
Kirin's
potential? I am
sure we have not seen it.
Sasuke seemed to have a great deal of faith in Kirin's usefulness in one on one battle with little to no attempts to keep the target in one place, even against Itachi (after all, did he not say himself that this was a jutsu he had developed for the sole purpose of defeating Itachi?), and seemed confused when it didn't work. He clearly thought it would
fast enough,
strong enough, etc... to
kill Itachi. This says to me that the
one time we saw it being used, Kirin was, perhaps, INCOMPLETE.
Now, however, let us come to
present time. We have a new, potentially
stupidly powerful Sasuke who will most likely make
very good use of Kirin; developing it in ways that will allow it to strike multiple times in lightning-quick succession... or with multiple bolts... maybe electrifying the area around it, creating a version of a much greater scale (which could perhaps be done in many other ways as well... after all, the ground being electrified isn't exactly close to perfect or even hard to avoid... a much bigger lightning bolt, if possible, would be far more effective I would think), etc.
Surely it will also be more powerful.
Coupled with Amaterasu to chase the opponent around, a good battlefield (a place where there isn't much space to run away, such as a canyon, a maze, a mountain, open water, or what have you, I see Kirin as being very,
very problematic and deadly to any opponent without the means to counter it, partially because I don't see a completely perfected, Sasuke-designed Kirin being something that would be easy to escape, prep time or no. And even with prep time, I mean come on. Susano'hello?
Susano'o eliminates the option to attack effectively during the prep time for most opponents, especially close-range specialists.
The Susano'o arrow (IF it is able to be fired whilst prepping Kirin... if not, probably still would be enough time if Sasuke just fired it right before, at least in my opinion) is quite hard to dodge.... and the Sharingan itself, let's not forget, allows Sasuke to see/know just about exactly where the struck target will end up. Stick em to a tree for all he cares, hell. If they aren't already dead from the arrow, which is most likely many times slower than Kirin and yet so damned fast, then anyone following my logic ought to know what comes next in this here scenario.
Kirin is fired now. Fried shinobi.
Perhaps to some that seemed like a long explanation, but go over it in your head after you fully understand it, and you will notice that any of the scenarios within that wall of coloured text would take very little time, and yet allow for much more time than it would take (most likely, and obviously depending on the opponent). Kirin is most certainly
NOT the most
POWERFUL jutsu, but is potentially one of the deadliest when used strategically. Sasuke, much like Shikamaru, is a
highly intelligent, calm/collected, and effective strategist... in case there is anyone who hasn't noticed.
Thanks to those of you who read this.