What exactly did you do? As with the old system, I would guess you first have to get all current particles with ParticleSystem.GetParticles, then remove the particle you want from that array somehow, and then reassign that new array back to the ParticleSystem (but read on).

In the old particle system (ParticleEmitter), instead of removing the particle physically from the array, it was enough to set its energy to 0. This way the ParticleEmitter will take care of the rest, recognize the particle als being dead/finished, and remove it itself from its internal particle array. I would assume you can do the same with Shuriken?

EDIT: I tested this now for myself. The Shuriken works the same as the old system, you can modify/remove/add individual particles. BUT the API call to get the existing particles is just plain weird and stupid, I have no idea why anyone would program it in such a way: Instead of simply returning the particles array, which you then can modify, you must provide your own array, which is passed to GetParticles(). After this call returns, your particles array has been filled with the information of the existing ParticleSystem. This is completely unintuitive, and would probably be frowned upon and discouraged in any programming guide, to call a function "GetXXX", but then have it modify an array you have to initialize and pass into it.

tl;dr: Try this example instead, it will work. Create a new ParticleSystem with default emission behaviour, and attach this script to it. (Note, when using the menu GameObject->CreateOther->ParticleSystem, the ParticleSystem will initially have an x=270 rotation, for whatever reason)

using UnityEngine;
using System.Collections;

public class ParticleSystemTest : MonoBehaviour {

    private ParticleSystem ps;

    void Start () {
        ps=GetComponent<ParticleSystem>();
    }

    void Update () {
        // initialize an array the size of our current particle count
        ParticleSystem.Particle[] particles=new ParticleSystem.Particle[ps.particleCount];

        // *pass* this array to GetParticles...
        int num=ps.GetParticles(particles);
        Debug.Log("Found "+num+" active particles.");
        for(int i=0;i<num;i++){
            if(particles[i].position.z>5) // large local z: let particle drop down
                particles[i].velocity-=Vector3.up*0.1f;
            if(particles[i].position.x>1) // positive x: make it red
                particles[i].color=Color.red;
            if(particles[i].position.x<-1) // negative x: make it die
                particles[i].lifetime=0;
        }
        // re-assign modified array
        ps.SetParticles(particles,num);
    }
}

So the more I research this, the more I'm beginning to believe that it's impossible to adjust the properties of a settled particle without the whole particle system starting the animation from scratch. If anyone could just confirm this that would be great. Then I can start investigating another option for my bouncing collectable coins...