It's soldy only trough Steam and Direct2Drive from what I've found out... Well, your interest ends there, doesn't it? :D
As for what makes it so good, just read the thread and watch trailers

From the look of things, probably Steam.
Also, unless things have changed recently, the retail version is only available in:
Russia, Ukraine, Belarus, Estonia, Latvia Lithuania, Moldavia, Kazakhstan, Kirghizia, Georgia, Armenia, Azerbaijan, Turkmenia, Tajikistan, Uzbekistan.
(source, question 7)

you'd think retail would be available in Chile

Bizarrely, the Direct2Drive version uses Steam for DRM, so no matter where you buy it you will end up having to use Steam.

I'm really enjoying it so far.
My only real complaints relate to the combat. It seems like you're just thrust from one fight to another, and aren't really given a chance to explore the surroundings much. At least in the beginning--I've only put an hour point five into it and the only area allowing a little exploration of the gorgeous environment was the small desert section.
The RPS review compared it to Jodorowsky's work, and I can actually see that, especially with the...what are they? Crowids of the Free? The insane fellow who walks only in a straight line...the bird-like man who plucks the eyes of anyone who spots him in order to be "invisible." Man...I love Jodorowsky.

I just beat it. Took me less than 3 hours. 2.9, it says, but .3 was used to demo it on another computer and another unknown bit to doing the first challenge. I did stop to look at things, too.
I thought this game should run at 4 hours minimum? Some fellah on the Steam boards said he did it in 3 and got shot down by everyone including the devs for exaggerating things.
Wow. That's short.

Short but sweet. it was cheap too if you got it the first day it went on sale. (and still 20 bucks ain't all that much anyway, though some would argue for just 3-4 hours it is much I'm sure).
The worlds creative style and just the privilege of seeing it is enough reason for me to have picked it up. And I dig the combat as well, reminds me of a game on the Xbox called Breakdown and Mirror's Edge. I'm hoping for more (good) first person beat-em-ups.

I asked em if it would come to Canada and they said its possible, they're still considering and discussing and such. So, maybe, maybe not for North America..
Personally, much as I love this game and want to support it, I wont buy from Steam or D2D. So I'm praying..

I recorded a video of Zeno Clash, it was pretty good, the audios kind of bad, but I think you'll like the video anyway
Zeno Clash, Multibreasted Enemies and Elephant Men

Hey, no Kosovo!

Guys the demo is out. Try it out if you haven't. It is REALLY PRETTY DAMN GOOD!
Also I'd like to talk about the Gayspot review as usual. Aside from Gayspot in-house retard reviewer Brett Todd doing his usual stint of not playing games for more than an hour before writing like the resident guru that he thinks he is, what the hell is he talking about in his review?????
http://www.gamespot.com/pc/action/zenoclash/review.html
I say, that is just so unfair to the indie community. This part really baffles me:
Fighting is just a matter of mashing the left and right mouse buttons to punch and kick while occasionally hitting the spacebar to block
What the hell? Are we playing a different game? Excuse me, what on earth is lil Bretty playing?
I'm...befuddled. Speechless. Stupidity of mankind doesn't get any higher than this.

Actually... I won all my encounters by just clicking left and right mouse buttons. Aside from that, the game is awesome.

(edited my above post for some phpbb code left in there from copying and pasting)
How do you win with button mashing? When I play, the enemies are pretty smart, dodging left and right and blocking your attacks fast. The block-counterattack is rather important especially when against slower but damage dealing enemies, making the need to plan your attacks even more important
From my play experience, this is definitely not Dynasty Warriors Special Edition

down arrow+strong punch ---> up arrow = win

I really like the game. Fighting system is among the best ones I've ever seen. And most definitely is one of the more immersive ones out there.
I really wish that the experience wasn't so guided though. The world they created is so vivid and alive that I always wanted to just have an opportunity to explore it and interact with it beyond introducing a fist to its face several times over.
Also for characters which are as recurring as in Zeno Clash they are surprisingly underdeveloped. The overall motivation for the conflict is clear but the individual stories are unfortunately never told (particularly of the family). What's even more bizarre is the fact that they do exist, they were thought out (or at least in a rudimentary state) as can be seen here:
[url=]http://www.zenoclash.com/profile_fathermother.jpg[/url]
Just never really implemented.
I really hope that the overall positive response will yield good sales for the game so that the inevitable sequel can be a little more encompassing. Though ultimately I'm just projecting here, I'll buy it regardless as I cant wait to have some more Zeno Clash!