How can I create a particle 'vortex' or implosion using Shuriken?

At first glance this would appear to be a fairly straightforward undertaking and yet I can find no resources that offer a solution.

The effect I am looking to achieve would resemble the standard cone-shaped particle system though running in reverse, where particles begin at their maximum distance from the system origin (this I've accomplished using the "Prewarm" property) and travel towards the origin until they die. A good real-world example would be a vacuum inhaling a cloud of smoke. The particles begin with zero velocity and would accelerate inwards towards the origin (point of suction).

However, I've had a great deal of difficulty implementing this. I've tried using a spherical emitter with inverted normals, a cone emitter with a negative starting velocity, really every combination of geometry and velocity manipulation but I've not been able to reproduce the effect I'm looking for.

My question is, has anybody been able to successfully create a vortex or implosion type particle effect in Shuriken? If so, how did you accomplish this? Additionally, I've been able to create a particle system with the desired effect using the legacy particle components, though I was advised to keep away from them as they are less efficient than the Shuriken system. Is this true? Are there any other drawbacks to using the legacy system that I should be aware of or is it just a matter of whatever works?

For clarification, the solution detailed in this question was the method I used to create the particle system using the legacy components:

http://answers.unity3d.com/questions/138207/inverted-particle-emitter.html