K2 first released its silverlight based process designer with the blackpoint product. It was probably the first ever workflow process designer built using silverlight for SharePoint.
With the upcoming K2 release called 4.5 a comprehensive update to this designer is in the works. I have been playing with the beta and the silverlight designer experience can only be described as “pure joy!”.
It is so intuitive, simple and visually pleasing. I have all the bits and pieces I need just there in front of me nicely organised : User browser, Inline Functions, SmartObjects, Datafields, SharePoint columns, New wizards, etc.
I have process templates, Sharing of process maps, Exporting to the K2 studio designer, and process guides if I get stuck. Needless to say I am impressed with this version.