I've been working with the trial beta for no more than 1-2 weeks, and still managed to setup an entire issue management system based on it for our operations department. The customization capabilities seem to be really unlimited, plus I was able to setup master detail views based on external data (some financial info is kept to systems outside MOSS) within minutes.
Boosts up sharepoint app development; definetely worth the price
-FAST (goodbye irritating post backs)
-WYSIWYG printing of the forms
-External data embedment
-Super: multiple forms based on custom conditions
perhaps one "drawback" (if you can call it that) is that it is "bound" to sharepoint. I would love to have it also as an independent product for building standalone silverlight forms outside sharepoint.