Wow.. what timing! I was writing this when I saw the other responses..
The STILLEN Rear Sway Bar has been released, and is currently shipping. It's a very easy installation, and will be a nice suspension upgrade from factory, and does fit both the coupe and sedan, 2.5/3.5L Altima's.
http://www.stillen.com/product...04235
LBC, it is non-adjustable in design, but it's not an overly aggressive bar, I really don't think it will make the vehicle too stiff, I really believe it's a nice upgrade.
Plus, these bars have built-in stops to eliminate side-to-side movement under hard cornering. Below is a picture of the bar.