Here is my review.
I really like the cool brewing bag overall. I have used it twice. The first time I filled the bag with water half way up my carboy. The second time I went with no water inside the bag, just air. It worked well in both cases.
With the water bath method I used less ice. I got the water bath water from an ice bath used when cooling the hot wort after boil. That limited the amount of ice needed on day one in the bag. I think I used 2 2L bottles on day one and then added 1 2L bottle per 24 hours on the following days. I think because the water bath and beer are a big thermal mass the temp holds steady this way and that is why it took less ice. But the water bath method has the annoyance of water which you have to dump at the end.
For the just air case I had to use a lot of ice (3 2L + 5 16.9oz bottles) to get it down to about 62F overnight. Once down there I used 2-3 2L bottles to stay at 64F during heavy fermentation on a 5.5G batch.
I change bottles every 24 hours. I could probably go longer but once per day is easy to remember.
I live in the deep south and my house is at 80F (which sucks for me and the beer). I am am easily able to keep the fermenter in the mid to low 60's with the cool brewing bag with both the water bath and just air methods.
The top of the bag does collapse onto your airlock. It does not put much pressure on the airlock when just sitting there but you do have to be careful when zipping up not to push on the airlock too hard. I did break an airlock. I had an old double bubble type. Those are tall and skinny unlike the 3 piece air locks which seem more short and squat. When I was closing the lid on the cooler I pulled down to get the zipper aligned and broke the air lock. It was an old air lock which had undergone its share off stress being removed from a bung (I always have trouble with that; they stick together too well). I am going to replace the airlock with a 3 piece one. Right now I am using a blow off tube into a 1G bucket of water sitting at the bottom of the bag. That works well since the bag lid presses down on the blow off tube and holds it in place. I may stick with this method and just use an air lock when the fermenter is sitting out of the bag aging beer (I don't cool it after fermentation ends).
Edit: I tried a large a plastic cup over the airlock one day and it easily held the top of the bag up away from the airlock. The day I broke my air lock I was going without the cup. The only issue with using the cup over the airlock was the bubbling was louder due to echoing. My wife didn't like that.
Here's a link to what I mean by double bubble airlock:
http://www.rebelbrewer.com/shoppingcart/products/Double-Bubble-Airlock.html
Here is a link to what I mean by 3 piece airlock:
http://www.rebelbrewer.com/shoppingcart/products/3%2dPiece-Airlock.html
Another great thing is the bag collapses and is easily stored when not in use.
I also like that the bag blocks out light. My kids leave the light on in the room where I ferment constantly. No more worrying about skunky beer.
Finally when I ordered the bag it shipped very quickly and I got an email with a tracking number without having to ask.
