In the noodles it doesn't change the flavor much. As a drink, the taste depends if there's lime or not... But you definitely want to add some flavors or make some kind of concoction because it's kind of earthy. Thais just put a lot of sugar and it tastes great but probably not healthy lol.
I'm surprised you didn't try it in Chiang Mai! Well.. not totally... They don't advertise very well. I totally found out about butterfly pea/ Anchan on my own because I randomly bought some of the dried flowers I saw in the supermarket.