I am wondering if there is any formal word or phrase for "wow factor" that shows same level of excitement positively.
stupendousness - so large or great that it amazes you. (M-W)
Webster's Definition of Specialty:a special or distinguishing feature or characteristic
wow factor: a quality or feature that is extremely impressive.
One alternative would be :
Charm : the power or quality of delighting, attracting, or fascinating others.
This feature has a wow factor that is irresistible
This feature has a charm that is irresistible
Astounding : causing amazement and wonder