Of course it still builds up heat in the case, it's not a blower cooler. To me, I think people are still confused about which cooler they have because not all of the 970's have the ACX 2.0. So it's hard to tell who actually has a 2.0 or not if they didn't realize it in the first place.

A couple of things...
 
Saying "I heard" when at this point they are not even in the wild yet makes me think someone is telling you things to just tell you, or you need to reference the reviewer saying this (Like a review site for an example).
 
For me, at 70%+ they seem to be the same. Each has it's own db rating of course, but I have found the original ACX to be worth the tiny bit of extra noise depending on the level needed. For example...
 
I would normally need to run the Blower type @ 65-70% when gaming in surround. Now with the ACX, with it being mere efficient, it is overall quieter because I can set them at 50% and run a degree or so cooler than I was with the blower version at 65-70%.
 
Noise wise I think this is because the blower has to push the air out the back of my case, and the ACX version db's are muted some what because they are inside a closed case.
 
But if one does not have sufficient fans to pull that heat out, it is counter productive. Not to mention those extra fans could cause even more unwanted noise...

Any updates on the ACX 2.0 rattle?

sadly i have to confirm it is loud. I have the SSC w/ ACX 2.0.  
 
the fans over 45% are incredibly loud.  for someone who has music running 90% of the time im at PC, a 5.1 setup... sound doesnt usually bother me.  
 
now the good.  Im running 40% fan in games..because the cooler itself does a great job.  The difference between 35-55% fan speed is only 12-14 degrees INGAME!!!!  Thus my custom fan profile barely changes at all from idle desktop to ingame... cuz im still seeing low to mid 60s ingame.   Only just messed with OCing but hit 1450 very easily, not much temp difference either.  
 
and also jus for the record I have a gtx770 classy ACX too. 

Loud.

Does anyone know if the ACX design on the currently available 970 cards is the same as the yet-to-be-released 980 cards? I can't find any solid information here.
 
Most customer feedback from the 970 series is overwhelmingly negative on the ACX cards, but I keep seeing people say that the 980 design will be different. Just not sure if that's correct or not.

Russ369
I have one. It creates TERRIBLE heat inside my case (I use a Fractal Node 304, so I probably should have gotten one of the blower coolers instead), terrible coin whine, I mean HORRID. My case sits right next to me on my case, my old evga 680 was quieter than this, and didnt have any coil whine. Im very disappointed with EVGA here, terrible quality.

What game were you testing the whine on? Was it an older game? How bad is it really though? Is it like this: or like this: . When your playing games with speakers on and the case door on, can you hear it? The open coolers are not designed for small cases like that, so your heat is to be expected. As far as the whine, I'd love to catch a recording of your issue. :-)