Personally, I would not call them cold air intakes. It has been documented by many others that they are essentially hot air intakes.
This means that you get lots more noise and possibly a bit less power, for your money.
The increased intake noise was very cool ... for about two days. (So was my new cap-firing cowboy sixgun I got for Christmas when I was eight. I grew up.)
On the I6, you might get a slight increase in power and only a bit more intake noise if you discard the CAI air box and use the stock airbox. All you have to do is to compare the components with a critical eye and you can see the CAI airbox is decidedly low tech. The stock GM airbox, on the other hand, is a fairly complex design that takes advantage of what is essentially an air-to-air intercooler.
I use the K&N with the stock airbox and I get a bit more growl on acceleration that is not obtrusive nor immature, and I get the advantage of a TRUE cold air intake, using the air-to-air intercooler design of the stock airbox. This gives me a very very slight increase in actual power, not seat-of-the-pants feel of increased power that is, in reality, just more noise.
The other issue I have with the CAI theory is that there is very little need for or an increase from a "ram air" effect. Free-breathing, double overhead cam, four-valve-per cylinder engines such as ours gain little from any increased ram effect because the engine draws in the air it needs; it does not need to ram it in. The engine will only take in the air it needs and no more.