has anyone done this or seen one? is it money well spent or money down the drain?

http://www.diversifiedcryogenics.com/gunbarrels.htm

JP Enterprises offers an upper with a cryo'd barrel...mine shoots 1/2" groups at 200 yds.  Hate to think it's all because of the cryo treatment but who knows...

This is something that bench rest shooters have been doing for years.  Seriously.  It is supposed to affect the grain of the alloy in the barrel and relieve internal stresses.  Does it work?  Case studies say yes.  Is it worth it?  That's entirely up to you.  You can spend a lot of money adding doo-dads to your gun.  The breaking point on how much to spend will probably be personal.  (If I had the cash, I'd do all kinds of crazy sh!^)  But, right now I'm just trying to scrape for an upper...

There's a lot of places that will do this for gun barrels so you may wanna shop around.  I know people who do it to brake disks on motorcycles too.  Supposedlly it helps prevent brake warping.