I have mixed feelings about this cocktail. On the one hand, it's pretty tasty, sweet, and very easy to drink. On the other hand, it's not very interesting, and is dangerously easy to drink. The pineapple really dominates, such that it tastes like you're drinking pineapple juice with a splash of rum, and the rum is so hidden that it tastes more like a gulper than a sipper. I can easily see someone drinking several of these in an hour and then wondering what hit them.
In revisiting this cocktail, I found I like bumping up the rum to 1.75 oz or 2 oz - it helps temper the sweetness of the pineapple with a stronger rum presence, and actually brings out more of the amaretto flavour.
This cocktail also benefits from more age on the rum, such that El Dorado 8 or 12 year work much better than 5.