Gear stars do work in battle
Since noone was doing it, I decided to just test it: Do attribute points from gear star levels have effect in combat? I tested it with a 32 attack hero, and putting a single piece of gear on the hero.
Note: they do not have an effect on training/producing/building/researching.
LVL6 Research / LVL 0 Star
http://img94.imageshack.us/img94/3334/star1cu.jpg
RESULT
http://img20.imageshack.us/img20/6121/star2o.jpg
LVL6 Research / LVL 11 Star
http://img31.imageshack.us/img31/5435/star3g.jpg
RESULT
http://img685.imageshack.us/img685/4688/star4y.jpg
CONCLUSION
Killed more enemy troops when I had 11 stars on the hero, all other factors the same. Stars do have an effect.
The test is not 100% fail proof, just wanted to do some quick testing. Will do some more testing soon. It does sure look like gear stars do 'work' in battle.