Mike Batchelor demonstrates how to have the particles in X-Particles 2 form various shapes over time with a smooth animation between each. X-Particles makes it simple to use and add goals with the control cover / target modifier.
New X-Particles project tutorial showing how to flow particles into different shapes over time
A new and recent release of X-Particles 2 can work with much larger particle counts using a new multithreaded component systems which includes a new multithreaded emitter. X-Particles 2 comes in the Standard Version for 149 euros or roughly $190, and a Pro version for 249 euros, roughly $330.