Benefits are more effeciency than electric heat, starting around 3:1 @ 40F ambient and dropping as ambient gets lower. It also compares favorably to gas and oil in areas with low electric cost.
Negatives are lower supply temps than gas or oil(feels cool to customer if they're used to oil or gas heat), lower life expectancy than straight A/C units, more parts that can go bad(higher repair costs), and cost more upfront than a straight a/c unit. It also loses it's capacity as the temp drops.
i'm sure there's more.....
If everything was always done "by the book"....the book would never change.
straight electric strip heat should not be used alone. the HP now are superior to the ones 15-20 years ago and normally cost 300 to 500 an will save that much in the first year if not 2. Also with the new energy codes in effect that most installers have ignored for the last 2 years you have to have R8 duct and more insultion than most builders will buy.