I guess not. It's good to have if you actually do get cursed, though. It also makes a classic Mario noise when you jump and plays a different song for each character. Other than that, no.
he's very useful in the pit of 100 trials in flipside and flopside when you get poisened or cursed, i actually use him more then i us barry or the othr unuseful pixls
I use her mainly for curing that annoying "ROAR!!!!" when using Bowser, the old 8-bit sound of his flaming breath alone is enough of a seller for me, but not to mention the symbols hidden around.
the only thing i really used piccolo for was to put the chain chomp to sleep. i dont remember what level it was in. it was when you had to play like an rpg. you didnt need to put them to sleep, but it was helpful if you had low health and few power-ups.