http://www.sweetwater.com/store/detail/ARC2/
$149.99 at Amazon, and 50% off in the customshop. For some reason it's $229 at Audiodeluxe.

Awesome... have wanted to ARC my space for years and this price is unresistable!!! Thanks, Clint!

BTW, recent controversy aside from a few users, I just spent an hour perusing the net 'verse and got reassured as to ARC 2's usefulness to my situation.  I have invested heavily in my songwriting tools and decent monitors (krk8's with krk sub)  but these must contend with a "cottage" rectangular multi-use living arrangement with modest trapping.   As I'm getting heavily into "lower frequency" ominous sounds these days (climate change music necessitates this thrust!) I want to preserve this edge and I just haven't been able to compensate/translate what I hear in the room to that which sounds good elsewhere...
 
I bought the SoundOnSound review of ARC2 and found it very positive. Also, http://therecordingrevolution.com/2013/07/22/ik-multimedia-arc-2-room-correction-plugin-review/ sums it up saying: "That being said, I honestly believe that at this point in my the life of my studio, the ARC 2 has been the best investment I’ve made in my studio this calendar year. Like speaker placement and acoustic treatment, it’s helped improve every other piece of gear I already own. I highly recommend it!
 
music radar also reviewed it and includes a vid from groove3 which was really helpful, discussing all the measurement issues, although it's of the original ARC...  http://www.musictech.net/2013/02/arc-2-review/
 
Mind you, I have been all over and in IK's face for a long time for their abandonment of users like me who bought lots of their stuff and no longer use 32bit bridge headaches any more... but as I'm going to be reconfiguring everything, including my room once my new DAW build is done, figure I'll try and see if ARC2 can help me create better mixes....
 
At $149... it's well worth the try.

Well ARC uses Audyssey room correction which in my opinion is 100% worth the price of admission. I actually run my computer out to a home theater receiver, to get MultEQ on surround sound and on all sources. It is a really solid technology that really does a good job helping out, particularly in the higher rez variants, which ARC is one of. It can't make a bad room great, but it can make a normal room better.

How useful would ARC be to someone who has absolutely no room treatment at all? Better than nothing, or worse than nothing?

better than nothing , first measurement will help you also to spot what the problem's are and try to cover them with a minimum of treatment (and some time just a great placement helps) 
 
This is thing is not an option and the best buy i tell my student , and the mic is descent for a lot of apllications ...don't hesitate !

sharke, I agree with Zo.  A lot depends on your room... btw, a youtube I just listened to is worthy...discusses all kind of nice interesting aspects/easy fixes/layout considerations, really basic that really helped me....
http://www.youtube.com/watch?v=W2SBmvBbIYI#t=39

I LOVE my ARC so much I tracked down a music player that supported VSTs just to be able to listen to music through it in my studio. I have heavy acoustic treatment, but the ARC changed everything. It's the biggest wow factor to visitors in the studio. I just play a song they are familiar with, hit the ARC2 button and suddenly they are hearing the music in a way they've never heard before. Sometimes you even notice parts that were not really present before.
 
I hear a lot of people that don't like it too, so YMMV.

smallstonefan
I LOVE my ARC so much I tracked down a music player that supported VSTs just to be able to listen to music through it in my studio. I have heavy acoustic treatment, but the ARC changed everything. It's the biggest wow factor to visitors in the studio. I just play a song they are familiar with, hit the ARC2 button and suddenly they are hearing the music in a way they've never heard before. Sometimes you even notice parts that were not really present before.
 
I hear a lot of people that don't like it too, so YMMV.

Listening to regular music through ARC through my monitors is the absolute best thing I have done.  Now all my mixes are A-B'ed with "real" music also through ARC in my studio space.  Makes all the difference.  Do you use Winamp with the VST add-on?

JUST PICKED IT UP.
 
TNX FOR HEADSUP