Dynamic field size and position.
The most notable and immediately useful addition is the introduction of resizable and movable fields. Since its inception, the product has had fixed size, and fixed position fields. What you see (at design time) is what you get (at run time), and in some versions, exactly. It has allowed us very fine control over the client user interface.
What has been missing is the ability to create more dynamic forms. The most obvious of these features would have to be the ability to resize a field if a form changes size, or if other fields need to be displayed. The next obvious feature would be to be able to move fields based on the appearance, or non-appearance, of other fields. In most Metastorm BPM ‘dynamic’ forms, we end up with a fair amount of blank wasted space when we need to hide fields.